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, respon ...
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 ...
in length and has three homologous
subunit
Subunit may refer to:
*Subunit HIV vaccine, a class of HIV vaccine
*Protein subunit, a protein molecule that assembles with other protein molecules
*Monomer, a molecule that may bind chemically to other molecules to form a polymer
*Sub-subunit, a ...
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 ...
residues cleaved off to produce mature C1QBP. C1QBP appears as a
monomer around 33 kDa on
SDS-PAGE
SDS-PAGE (sodium dodecyl sulfate–polyacrylamide gel electrophoresis) is a discontinuous electrophoretic system developed by Ulrich K. Laemmli which is commonly used as a method to separate proteins with molecular masses between 5 and 250 kDa. ...
gel under both reducing and nonreducing condition but migrates as a
trimer on
size-exclusion chromatography (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, macr ...
structure of C1QBP at 2.25 Ã… 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 Ã… in diameter. Each Subunit of C1QBP has seven
β-strand (β1- β7) and three
α-helices (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 with
Protein kinase D1,
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 ...
,
,
[ PKC alpha][ and Protein kinase Mζ.][
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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