Complement component 1 Q subcomponent-binding protein, mitochondrial 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 ''C1QBP''
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 ...
.
The human complement subcomponent C1q associates with C1r and C1s in order to yield the first component of the serum complement system. The protein encoded by this gene is known to bind to the globular heads of C1q molecules and inhibit C1 activation. This protein has also been identified as the p32 subunit of pre-mRNA splicing factor SF2, as well as a
hyaluronic acid-binding protein.
Protein subunit
C1QBP is 282
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
in length and has three homologous
subunit with its N-terminal 73
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
residues cleaved off to produce mature C1QBP. C1QBP appears as a
monomer
In chemistry, a monomer ( ; '' mono-'', "one" + ''-mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
...
around 33 kDa on
SDS-PAGE
SDS-PAGE (sodium dodecyl sulfate–polyacrylamide gel electrophoresis) is a Discontinuous electrophoresis, discontinuous electrophoretic system developed by Ulrich K. Laemmli which is commonly used as a method to separate proteins with molecular m ...
gel under both reducing and nonreducing condition but migrates as a
trimer on
size-exclusion chromatography
Size-exclusion chromatography (SEC), also known as molecular sieve chromatography, is a chromatographic method in which molecules in solution are separated by their size, and in some cases molecular weight. It is usually applied to large molecules ...
(gel filtration).
Protein structure
The
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...
structure of C1QBP at 2.25 Å resolution shows a homotrimeric ring displaying
symmetry. The individual subunits are held together by noncovalent interactions and forms a doughnut shaped
quaternary structure
Protein quaternary structure is the fourth (and highest) classification level of protein structure. Protein quaternary structure refers to the structure of proteins which are themselves composed of two or more smaller protein chains (also refe ...
with a central cavity of 20 Å in diameter. Each Subunit of C1QBP has seven
β-strand
The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a g ...
(β1- β7) and three
α-helices
The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues ear ...
(α1- α3). C1QBP is negatively charged on its soluble face while the membrane face is predominantly positively charged.
Interactions
C1QBP 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
Protein kinase D1
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, respond ...
,
BAT2
Large proline-rich protein BAT2 is a protein that in humans is encoded by the ''BAT2'' gene.
Function
A cluster of genes, BAT1-BAT5, has been localized in the vicinity of the genes for TNF alpha and TNF beta. These genes are all within the h ...
,
PRKCD
Protein kinase C delta type (or PKC-δ) is an enzyme that in humans is encoded by the ''PRKCD'' gene.
Function
Protein kinase C (PKC) is a family of serine- and threonine-specific protein kinases that can be activated by the second messeng ...
,
[ ]PKC alpha
Protein kinase C alpha (PKCα) is an enzyme that in humans is encoded by the ''PRKCA'' gene.
Function
Protein kinase C (PKC) is a family of serine- and threonine-specific protein kinases that can be activated by calcium and the second messeng ...
[ and ]Protein kinase Mζ
Protein kinase C, zeta (PKCζ), also known as PRKCZ, is a protein in humans that is encoded by the ''PRKCZ'' gene. The PRKCZ gene encodes at least two alternative transcripts, the full-length PKCζ and an N-terminal truncated form PKMζ. PKMζ i ...
.[
Other interacting partners of C1QBP include protein domains from pathogens such as bacteria, virus and plasmodium falciparum. Plasma proteins including fibrinogen, FXII and HK have been demonstrated to interact with C1QBP in a zinc dependent manner,. Recently, a tumour homing peptide, LyP-1(CGNKRTRGC) has been shown to selectively bind to C1QBP in tumour expressing cells.]
References
Further reading
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External links
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{{gene-17-stub