The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an
organelle found in most
eukaryotic
Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...
cells.
Part of the
endomembrane system
The endomembrane system is composed of the different membranes (endomembranes) that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles. In eukaryotes ...
in the
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...
, it
packages proteins into
membrane-bound
A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the c ...
vesicle
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry)
In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form nat ...
s inside the cell before the vesicles are sent to their destination. It resides at the intersection of the secretory, lysosomal, and
endocytic
Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material. E ...
pathways. It is of particular importance in processing
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s for
secretion, containing a set of
glycosylation enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s that attach various sugar monomers to proteins as the proteins move through the apparatus.
It was identified in 1897 by the Italian scientist
Camillo Golgi
Camillo Golgi (; 7 July 184321 January 1926) was an Italian biologist and pathologist known for his works on the central nervous system. He studied medicine at the University of Pavia (where he later spent most of his professional career) betwee ...
and was named after him in 1898.
Discovery
Owing to its large size and distinctive structure, the Golgi apparatus was one of the first
organelles to be discovered and observed in detail. It was discovered in 1898 by Italian physician
Camillo Golgi
Camillo Golgi (; 7 July 184321 January 1926) was an Italian biologist and pathologist known for his works on the central nervous system. He studied medicine at the University of Pavia (where he later spent most of his professional career) betwee ...
during an investigation of the
nervous system
In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes ...
.
After first observing it under his
microscope
A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...
, he termed the structure as ''apparato reticolare interno'' ("internal reticular apparatus"). Some doubted the discovery at first, arguing that the appearance of the structure was merely an optical illusion created by the observation technique used by Golgi. With the development of modern microscopes in the twentieth century, the discovery was confirmed.
Early references to the Golgi apparatus referred to it by various names including the "Golgi–Holmgren apparatus", "Golgi–Holmgren ducts", and "Golgi–Kopsch apparatus".
The term "Golgi apparatus" was used in 1910 and first appeared in the scientific literature in 1913, while "Golgi complex" was introduced in 1956.
Subcellular localization
The subcellular localization of the Golgi apparatus varies among
eukaryotes. In mammals, a single Golgi apparatus is usually located near the
cell nucleus, close to the
centrosome
In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle prog ...
. Tubular connections are responsible for linking the stacks together. Localization and tubular connections of the Golgi apparatus are dependent on
microtubules. In experiments it is seen that as microtubules are depolymerized the Golgi apparatuses lose mutual connections and become individual stacks throughout the
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...
.
In
yeast
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...
, multiple Golgi apparatuses are scattered throughout the cytoplasm (as observed in ''
Saccharomyces cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have b ...
''). In
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...
s, Golgi stacks are not concentrated at the centrosomal region and do not form Golgi ribbons.
Organization of the plant Golgi depends on
actin
Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ov ...
cables and not microtubules.
The common feature among Golgi is that they are adjacent to
endoplasmic reticulum (ER) exit sites.
Structure
![Golgi apparatus (borderless version)-en](https://upload.wikimedia.org/wikipedia/commons/4/42/Golgi_apparatus_%28borderless_version%29-en.svg)
In most eukaryotes, the Golgi apparatus is made up of a series of compartments and is a collection of fused, flattened membrane-enclosed disks known as
cisternae (singular: ''cisterna'', also called "dictyosomes"), originating from vesicular clusters that bud off the
endoplasmic reticulum. A mammalian cell typically contains 40 to 100 stacks of cisternae.
Between four and eight cisternae are usually present in a stack; however, in some
protists as many as sixty cisternae have been observed.
This collection of cisternae is broken down into ''cis'', medial, and ''trans'' compartments, making up two main networks: the cis Golgi network (CGN) and the trans Golgi network (TGN). The CGN is the first cisternal structure, and the TGN is the final, from which
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s are packaged into
vesicle
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry)
In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form nat ...
s destined to
lysosome
A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane pr ...
s, secretory vesicles, or the cell surface. The TGN is usually positioned adjacent to the stack, but can also be separate from it. The TGN may act as an early
endosome
Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are parts of endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane can ...
in
yeast
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...
and
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclu ...
s.
There are structural and organizational differences in the Golgi apparatus among eukaryotes. In some yeasts, Golgi stacking is not observed. ''
Pichia pastoris
''Pichia pastoris'' is a species of methylotrophic yeast. It was found in the 1960s, with its feature of using methanol as a source of carbon and energy. After years of study, ''P. pastoris'' was widely used in biochemical research and biotech ...
'' does have stacked Golgi, while ''
Saccharomyces cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have b ...
'' does not.
In plants, the individual stacks of the Golgi apparatus seem to operate independently.
The Golgi apparatus tends to be larger and more numerous in cells that synthesize and secrete large amounts of substances; for example, the
antibody
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
-secreting
plasma B cell
Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B lymphocytes and secrete large quantities of proteins called antibodies in response to being presented specific substa ...
s of the immune system have prominent Golgi complexes.
In all eukaryotes, each cisternal stack has a ''cis'' entry face and a ''trans'' exit face. These faces are characterized by unique morphology and
biochemistry
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
.
Within individual stacks are assortments of
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s responsible for selectively modifying protein cargo. These modifications influence the fate of the protein. The compartmentalization of the Golgi apparatus is advantageous for separating enzymes, thereby maintaining consecutive and selective processing steps: enzymes catalyzing early modifications are gathered in the ''cis'' face cisternae, and enzymes catalyzing later modifications are found in ''trans'' face cisternae of the Golgi stacks.
Function
![0314_Golgi_Apparatus_a_en](https://upload.wikimedia.org/wikipedia/commons/f/f0/0314_Golgi_Apparatus_a_en.png)
The Golgi apparatus is a major collection and dispatch station of protein products received from the
endoplasmic reticulum (ER). Proteins synthesized in the ER are packaged into
vesicle
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry)
In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form nat ...
s, which then fuse with the Golgi apparatus. These cargo proteins are modified and destined for secretion via
exocytosis or for use in the cell.
In this respect, the Golgi can be thought of as similar to a post office: it packages and labels items which it then sends to different parts of the cell or to the
extracellular space
Extracellular space refers to the part of a multicellular organism outside the cells, usually taken to be outside the plasma membranes, and occupied by fluid. This is distinguished from intracellular space, which is inside the cells.
The compos ...
. The Golgi apparatus is also involved in
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...
transport and
lysosome
A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane pr ...
formation.
The structure and function of the Golgi apparatus are intimately linked. Individual stacks have different assortments of enzymes, allowing for progressive processing of cargo proteins as they travel from the cisternae to the trans Golgi face.
Enzymatic reactions within the Golgi stacks occur exclusively near its membrane surfaces, where enzymes are anchored. This feature is in contrast to the ER, which has soluble proteins and enzymes in its
lumen. Much of the enzymatic processing is
post-translational modification
Post-translational modification (PTM) is the covalent and generally enzymatic modification of proteins following protein biosynthesis. This process occurs in the endoplasmic reticulum and the golgi apparatus. Proteins are synthesized by ribos ...
of proteins. For example, phosphorylation of
oligosaccharide
An oligosaccharide (/ˌɑlɪgoʊˈsækəˌɹaɪd/; from the Greek ὀλίγος ''olígos'', "a few", and σάκχαρ ''sácchar'', "sugar") is a saccharide polymer containing a small number (typically two to ten) of monosaccharides (simple sug ...
s on lysosomal proteins occurs in the early CGN.
''Cis''
cisterna
A cisterna (plural cisternae) is a flattened membrane vesicle found in the endoplasmic reticulum and Golgi apparatus. Cisternae are an integral part of the packaging and modification processes of proteins occurring in the Golgi.
Function
Protei ...
are associated with the removal of
mannose
Mannose is a sugar monomer of the aldohexose series of carbohydrates. It is a C-2 epimer of glucose. Mannose is important in human metabolism, especially in the glycosylation of certain proteins. Several congenital disorders of glycosylation ...
residues.
Removal of mannose residues and addition of
N-acetylglucosamine occur in medial cisternae.
Addition of
galactose
Galactose (, '' galacto-'' + ''-ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molecu ...
and
sialic acid occurs in the ''trans'' cisternae.
Sulfation
Sulfation is the chemical reaction that entails the addition of SO3 group. In principle, many sulfations would involve reactions of sulfur trioxide (SO3). In practice, most sulfations are effected less directly. Regardless of the mechanism, the ...
of
tyrosine
-Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the G ...
s and
carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or m ...
s occurs within the TGN.
Other general post-translational modifications of proteins include the addition of carbohydrates (
glycosylation)
and phosphates (
phosphorylation). Protein modifications may form a
signal sequence that determines the final destination of the protein. For example, the Golgi apparatus adds a
mannose-6-phosphate label to proteins destined for
lysosome
A lysosome () is a membrane-bound organelle found in many animal cells. They are spherical vesicles that contain hydrolytic enzymes that can break down many kinds of biomolecules. A lysosome has a specific composition, of both its membrane pr ...
s. Another important function of the Golgi apparatus is in the formation of
proteoglycans
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to which ...
. Enzymes in the Golgi append proteins to
glycosaminoglycan
Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case ...
s, thus creating proteoglycans.
Glycosaminoglycans are long unbranched
polysaccharide molecules present in the
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...
of animals.
Vesicular transport
The
vesicle
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry)
In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form nat ...
s that leave the
rough endoplasmic reticulum
The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough endoplasmic reticulum ( ...
are transported to the ''cis'' face of the Golgi apparatus, where they fuse with the Golgi membrane and empty their contents into the
lumen. Once inside the lumen, the molecules are modified, then sorted for transport to their next destinations.
Those proteins destined for areas of the cell other than either the
endoplasmic reticulum or the Golgi apparatus are moved through the Golgi
cisternae towards the ''trans'' face, to a complex network of membranes and associated vesicles known as the ''trans-Golgi network'' (TGN). This area of the Golgi is the point at which proteins are sorted and shipped to their intended destinations by their placement into one of at least three different types of vesicles, depending upon the
signal sequence they carry.
Current models of vesicular transport and trafficking
Model 1: Anterograde vesicular transport between stable compartments
* In this model, the Golgi is viewed as a set of stable compartments that work together. Each compartment has a unique collection of
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s that work to modify
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
cargo. Proteins are delivered from the ER to the ''cis'' face using
COPII
The Coat Protein Complex II, or COPII, is a group of proteins that facilitate the formation of vesicles to transport proteins from the endoplasmic reticulum to the Golgi apparatus or endoplasmic-reticulum–Golgi intermediate compartment. This ...
-coated
vesicle
Vesicle may refer to:
; In cellular biology or chemistry
* Vesicle (biology and chemistry)
In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form nat ...
s. Cargo then progress toward the ''trans'' face in
COPI-coated vesicles. This model proposes that COPI vesicles move in two directions:
anterograde vesicles carry
secretory protein
A secretory protein is any protein, whether it be endocrine or exocrine, which is secreted by a cell. Secretory proteins include many hormones, enzymes, toxins, and antimicrobial peptides.
Secretory proteins are synthesized in the endoplasmic ret ...
s, while
retrograde vesicles recycle Golgi-specific trafficking proteins.
** Strengths: The model explains observations of compartments, polarized distribution of enzymes, and waves of moving vesicles. It also attempts to explain how Golgi-specific enzymes are recycled.
** Weaknesses: Since the amount of COPI vesicles varies drastically among types of cells, this model cannot easily explain high trafficking activity within the Golgi for both small and large cargoes. Additionally, there is no convincing evidence that COPI vesicles move in both the anterograde and retrograde directions.
* This model was widely accepted from the early 1980s until the late 1990s.
Model 2: Cisternal progression/maturation
* In this model, the fusion of COPII vesicles from the ER begins the formation of the first ''cis''-
cisterna
A cisterna (plural cisternae) is a flattened membrane vesicle found in the endoplasmic reticulum and Golgi apparatus. Cisternae are an integral part of the packaging and modification processes of proteins occurring in the Golgi.
Function
Protei ...
of the Golgi stack, which progresses later to become mature TGN cisternae. Once matured, the TGN cisternae dissolve to become secretory vesicles. While this progression occurs, COPI vesicles continually recycle Golgi-specific proteins by delivery from older to younger cisternae. Different recycling patterns may account for the differing biochemistry throughout the Golgi stack. Thus, the compartments within the Golgi are seen as discrete kinetic stages of the maturing Golgi apparatus.
** Strengths: The model addresses the existence of Golgi compartments, as well as differing biochemistry within the cisternae, transport of large proteins, transient formation and disintegration of the cisternae, and retrograde mobility of native Golgi proteins, and it can account for the variability seen in the structures of the Golgi.
** Weaknesses: This model cannot easily explain the observation of fused Golgi networks, tubular connections among cisternae, and differing kinetics of secretory cargo exit.
Model 3: Cisternal progression/maturation with heterotypic tubular transport
* This model is an extension of the cisternal progression/maturation model. It incorporates the existence of tubular connections among the cisternae that form the Golgi ribbon, in which cisternae within a stack are linked. This model posits that the tubules are important for bidirectional traffic in the ER-Golgi system: they allow for fast anterograde traffic of small cargo and/or the retrograde traffic of native Golgi proteins.
** Strengths: This model encompasses the strengths of the cisternal progression/maturation model that also explains rapid trafficking of cargo, and how native Golgi proteins can recycle independently of COPI vesicles.
** Weaknesses: This model cannot explain the transport kinetics of large protein cargo, such as
collagen. Additionally, tubular connections are not prevalent in plant cells. The roles that these connections have can be attributed to a cell-specific specialization rather than a universal trait. If the membranes are continuous, that suggests the existence of mechanisms that preserve the unique biochemical gradients observed throughout the Golgi apparatus.
Model 4: Rapid partitioning in a mixed Golgi
* This rapid partitioning model is the most drastic alteration of the traditional vesicular trafficking point of view. Proponents of this model hypothesize that the Golgi works as a single unit, containing domains that function separately in the processing and export of protein cargo. Cargo from the ER move between these two domains, and randomly exit from any level of the Golgi to their final location. This model is supported by the observation that cargo exits the Golgi in a pattern best described by exponential kinetics. The existence of domains is supported by fluorescence microscopy data.
** Strengths: Notably, this model explains the exponential kinetics of cargo exit of both large and small proteins, whereas other models cannot.
** Weaknesses: This model cannot explain the transport kinetics of large protein cargo, such as collagen. This model falls short on explaining the observation of discrete compartments and polarized biochemistry of the Golgi cisternae. It also does not explain formation and disintegration of the Golgi network, nor the role of COPI vesicles.
Model 5: Stable compartments as cisternal model progenitors
* This is the most recent model. In this model, the Golgi is seen as a collection of stable compartments defined by
Rab (G-protein)
The Rab family of proteins is a member of the Ras superfamily of small G proteins. Approximately 70 types of Rabs have now been identified in humans. Rab proteins generally possess a GTPase fold, which consists of a six-stranded beta sheet which ...
GTPase
GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a pro ...
s.
** Strengths: This model is consistent with numerous observations and encompasses some of the strengths of the cisternal progression/maturation model. Additionally, what is known of the Rab GTPase roles in mammalian endosomes can help predict putative roles within the Golgi. This model is unique in that it can explain the observation of "megavesicle" transport intermediates.
** Weaknesses: This model does not explain morphological variations in the Golgi apparatus, nor define a role for COPI vesicles. This model does not apply well for plants, algae, and fungi in which individual Golgi stacks are observed (transfer of domains between stacks is not likely). Additionally, megavesicles are not established to be intra-Golgi transporters.
Though there are multiple models that attempt to explain vesicular traffic throughout the Golgi, no individual model can independently explain all observations of the Golgi apparatus. Currently, the cisternal progression/maturation model is the most accepted among scientists, accommodating many observations across
eukaryotes. The other models are still important in framing questions and guiding future experimentation. Among the fundamental unanswered questions are the directionality of COPI vesicles and role of Rab GTPases in modulating protein cargo traffic.
Brefeldin A
Brefeldin A
Brefeldin A is a lactone antiviral produced by the fungus '' Penicillium brefeldianum''. Brefeldin A inhibits protein transport from the endoplasmic reticulum to the golgi complex indirectly by preventing association of COP-I coat to the Golgi me ...
(BFA) is a fungal
metabolite used experimentally to disrupt the secretion pathway as a method of testing Golgi function.
BFA blocks the activation of some
ADP-ribosylation factors (
ARF
ARF may refer to:
Organizations
* Advertising Research Foundation
* Animal Rescue Foundation
* Armenian Revolutionary Federation
* ASEAN Regional Forum
People
* Cahit Arf (1910–1997), Turkish mathematician
Science, medicine, and mathematics
* ...
s).
ARFs are small
GTPase
GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a pro ...
s which regulate vesicular trafficking through the binding of COPs to
endosome
Endosomes are a collection of intracellular sorting organelles in eukaryotic cells. They are parts of endocytic membrane transport pathway originating from the trans Golgi network. Molecules or ligands internalized from the plasma membrane can ...
s and the Golgi.
BFA inhibits the function of several
guanine nucleotide exchange factor
Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). A variety of unrelated struc ...
s (GEFs) that mediate GTP-binding of ARFs.
Treatment of cells with BFA thus disrupts the secretion pathway, promoting disassembly of the Golgi apparatus and distributing Golgi proteins to the endosomes and ER.
Gallery
File:YeastGolgiMovieeLifec.ogg, Yeast Golgi dynamics. Green labels early Golgi, red labels late Golgi.
File:GolgiRibbonc.jpg, Two Golgi stacks connected as a ribbon in a mouse cell. Taken fro
the movie
File:GolgiScyl1c.jpg, Three-dimensional projection of a mammalian Golgi stack imaged by confocal microscopy
Confocal microscopy, most frequently confocal laser scanning microscopy (CLSM) or laser confocal scanning microscopy (LCSM), is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a s ...
and volume surface rendered using Imaris
Bitplane is a provider of software for 3D and 4D image analysis for the life sciences. Founded in December 1992, Bitplane operates out of three offices in Zürich, Switzerland, Belfast, United Kingdom, and South Windsor, Connecticut, United Stat ...
software. Taken fro
the movie
References
External links
*
{{DEFAULTSORT:Golgi Apparatus
Organelles