Structural highlights
Function
[ASIP_HUMAN] Involved in the regulation of melanogenesis. The binding of ASP to MC1R precludes alpha-MSH initiated signaling and thus blocks production of cAMP, leading to a down-regulation of eumelanogenesis (brown/black pigment) and thus increasing synthesis of pheomelanin (yellow/red pigment). In higher primates, agouti may affect the quality of hair pigmentation rather than its pattern of deposition. Could well play a role in neuroendocrine aspects of melanocortin action. May have some functional role in regulating the lipid metabolism with adipocytes.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
Expression of the agouti signaling protein (ASIP) during hair growth produces the red/yellow pigment pheomelanin. ASIP, and its neuropeptide homolog the agouti-related protein (AgRP) involved in energy balance, are novel, paracrine signaling molecules that act as inverse agonists at distinct subsets of melanocortin receptors. Ubiquitous ASIP expression in mice gives rise to a pleiotropic phenotype characterized by a uniform yellow coat color, obesity, overgrowth, and metabolic derangements similar to type II diabetes in humans. Here we report the synthesis and NMR structure of ASIP's active, cysteine-rich, C-terminal domain. ASIP adopts the inhibitor cystine knot fold and, along with AgRP, are the only known mammalian proteins in this structure class. Moreover, ASIP populates two distinct conformers resulting from a cis peptide bond at Pro102-Pro103 and a coexistence of cis/trans isomers of Ala104-Pro105. Pharmacologic studies of Pro-->Ala mutants demonstrate that the minor conformation with two cis peptide bonds is responsible for activity at all MCRs. The loop containing the heterogeneous Ala-Pro peptide bond is conserved in mammals, and suggests that ASIP is either trapped by evolution in this unusual configuration or possesses function outside of strict MCR antagonism.
Structures of the agouti signaling protein.,McNulty JC, Jackson PJ, Thompson DA, Chai B, Gantz I, Barsh GS, Dawson PE, Millhauser GL J Mol Biol. 2005 Mar 4;346(4):1059-70. Epub 2005 Jan 25. PMID:15701517[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ McNulty JC, Jackson PJ, Thompson DA, Chai B, Gantz I, Barsh GS, Dawson PE, Millhauser GL. Structures of the agouti signaling protein. J Mol Biol. 2005 Mar 4;346(4):1059-70. Epub 2005 Jan 25. PMID:15701517 doi:10.1016/j.jmb.2004.12.030
