Golgi reassembly-stacking protein of 55 k Da (GRASP55) also known as golgi reassembly-stacking protein 2 (GORASP2) is a

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, res ...

that in humans is encoded by the ''GORASP2''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

. It was identified by its homology with GRASP65 and the protein's amino acid sequence was determined by analysis of a molecular clone of its

complementary DNA In genetics, complementary DNA (cDNA) is DNA synthesized from a single-stranded RNA (e.g., messenger RNA (mRNA) or microRNA (miRNA)) template in a reaction catalyzed by the enzyme reverse transcriptase. cDNA is often used to express a spec ...

. The first ( N-terminus) 212

amino acid residues Protein structure is the three-dimensional arrangement of atoms in an amino acid-chain molecule. Proteins are polymers specifically polypeptides formed from sequences of amino acids, the monomers of the polymer. A single amino acid monomer may ...

of GRASP55 are highly homologous to those of GRASP65, but the remainder of the 454 amino acid residues are highly diverged from GRASP65. The conserved region is known as the GRASP domain, and it is conserved among GRASPs of a wide variety of eukaryotes, but not

plants 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 exclude ...

. The C-terminus portion of the molecule is called the ''SPR domain'' ( serine, proline-rich). GRASP55 is more closely related to homologues in other species, suggesting that GRASP55 is ancestral to GRASP65. GRASP55 is found associated with the medial and trans cisternae of the

Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ...

Function

GRASP55 is involved in establishing the structure of the Golgi apparatus. It is a

peripheral membrane protein Peripheral membrane proteins, or extrinsic membrane proteins, are membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the perip ...

located on the Golgi

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 ...

, and it can bind to another GRASP55 located on an adjacent cisterna through the GRASP domain, thus linking the cisternae together through multiple

protein–protein interaction Protein–protein interactions (PPIs) are physical contacts of high specificity established between two or more protein molecules as a result of biochemical events steered by interactions that include electrostatic forces, hydrogen bonding and th ...

s. GRASP55 is attached to the membrane in two ways; it is myristylated, which attaches it directly to the

lipid bilayer The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells. The cell membranes of almost all organisms and many vir ...

; it is also bound indirectly by binding to golgin-45, which binds to a Rab protein, which itself is lipidated and thus anchored to the membrane. The structure of the Golgi is disrupted during mitosis, and phosphorylation of the SPR domains of GRASP55 and GRASP65 regulate that disruption, GRASP55 may also be involved in forming Golgi ribbons, but the evidence is mixed.

Other interactions

GRASP55 has been shown to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization using innovative strategies to advocate for the legal and human rights of children with intersex traits. The organizati ...

with

TGF alpha Transforming growth factor alpha (TGF-α) is a protein that in humans is encoded by the TGFA gene. As a member of the epidermal growth factor (EGF) family, TGF-α is a mitogenic polypeptide. The protein becomes activated when binding to receptors ...

, TMED2 and

GOLGA2 Golgin subfamily A member 2 is a protein that in humans is encoded by the ''GOLGA2'' gene. Function The Golgi apparatus, which participates in glycosylation and transport of proteins and lipids in the secretory pathway, consists of a series of ...

. :

Function

Other interactions

References

Further reading