| Granin (chromogranin or secretogranin) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Structure of SS-cyclized catestatin fragment from chromogranin A. [1] | |||||||||
| Identifiers | |||||||||
| Symbol | Granin | ||||||||
| Pfam | PF01271 | ||||||||
| InterPro | IPR001990 | ||||||||
| PROSITE | PDOC00365 | ||||||||
| SCOP2 | 1cfk / SCOPe / SUPFAM | ||||||||
| OPM superfamily | 282 | ||||||||
| OPM protein | 1lv4 | ||||||||
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Granin (chromogranin and secretogranin) is a protein family of regulated secretory proteins ubiquitously found in the cores of amine and peptide hormone and neurotransmitter dense-core secretory vesicles. [2]
Granins (chromogranins or secretogranins) are acidic proteins and are present in the secretory granules of a wide variety of endocrine and neuro-endocrine cells. The exact function(s) of these proteins is not yet settled but there is evidence that granins function as pro-hormones, giving rise to an array of peptide fragments for which autocrine, paracrine, and endocrine activities have been demonstrated in vitro and in vivo. The intracellular biochemistry of granins includes binding of Ca2+, ATP and catecholamines (epinephrine, norepinephrine) within the hormone storage vesicle core. There is also evidence that CgA, and perhaps other granins, regulate the biogenesis of dense-core secretory vesicles and hormone sequestration in neuroendocrine cells.
Apart from their subcellular location and the abundance of acidic residues (Asp and Glu), these proteins do not share many structural similarities. Only one short region, located in the C-terminal section, is conserved in all these proteins. Chromogranins and secretogranins together share a C-terminal motif, whereas chromogranins A and B share a region of high similarity in their N-terminal section; this region includes two cysteine residues involved in a disulfide bond.
There are considerable differences in the amino acid composition between different animals. Commercial assays for measuring human CGA can usually not be used for measuring CGA in samples from other species. Some specific parts of the molecule have a higher degree of amino acid homology and methods where the antibodies are directed against specific epitopes can be used to measure samples from different animals. [3] Region-specific assays measuring defined parts of CGA, CGB and SG2 can be used for measurements in samples from cats and dogs. [4] [5] [6] [7]
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Some other proteins are also proposed to belong to the granins based on their physico-chemical properties. These include NESP55 (SgVI), VGF (SgVII), and ProSAAS (SgVIII). [8]
CGA may refer to:
Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is synthesized in corticotrophs of the anterior pituitary from the 267-amino-acid-long polypeptide precursor pre-pro-opiomelanocortin (pre-POMC), by the removal of a 26-amino-acid-long signal peptide sequence during translation. POMC is part of the central melanocortin system.
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Parathyroid chief cells are one of the two cell types of the parathyroid glands, along with oxyphil cells. The chief cells are much more prevalent in the parathyroid gland than the oxyphil cells. It is perceived that oxyphil cells may be derived from chief cells at puberty, as they are not present at birth like chief cells.
Synaptophysin, also known as the major synaptic vesicle protein p38, is a protein that in humans is encoded by the SYP gene.
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In biology, cell signaling is the process by which a cell interacts with itself, other cells, and the environment. Cell signaling is a fundamental property of all cellular life in prokaryotes and eukaryotes.
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Chromogranin-A (CgA) or parathyroid secretory protein 1 is encoded in the human by the gene CHGA. Cga is a member of the granin family of neuroendocrine secretory proteins. As such, it is located in secretory vesicles of neurons and endocrine cells such as islet beta cell secretory granules in the pancreas.
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SCG2, also called secretogranin II (chromogranin C), is a protein which in humans is encoded by the SCG2 gene.
Neuroendocrine protein 7B2 is a protein that in humans is encoded by the SCG5 gene. The protein expressed by this gene is widely distributed in neuroendocrine tissues. It functions as a chaperone protein for the proprotein convertase PC2 by blocking the aggregation of this protein, and is required for the production of an active PC2 enzyme. It is an intrinsically disordered protein that may also function as a chaperone for other aggregating secretory proteins in addition to proPC2. 7B2 has been identified in vertebrates and in invertebrates as low as flatworms and insects. It is also called Sgne1 and Secretogranin V. In C. elegans, it was originally called e7B2 and then renamed Seven B Two. There is a Pfam entry for this protein: Secretogranin_V (PF05281).
Secretogranin III, also known as SCG3, is a protein which in humans is encoded by the SCG3 gene.
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