Somatomedin B domain | |||||||||||
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Identifiers | |||||||||||
Symbol | Somatomedin_B | ||||||||||
Pfam | PF01033 | ||||||||||
InterPro | IPR001212 | ||||||||||
SMART | SO | ||||||||||
PROSITE | PDOC00453 | ||||||||||
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Somatomedin B is a serum factor of unknown function, is a small cysteine-rich peptide, derived proteolytically from the N-terminus of the cell-substrate adhesion protein vitronectin. [1] Cys-rich somatomedin B-like domains are found in a number of proteins, [2] including plasma-cell membrane glycoprotein (which has nucleotide pyrophosphate and alkaline phosphodiesterase I activities) [3] and placental protein 11 (which appears to possess amidolytic activity).
The SMB domain of vitronectin has been demonstrated to interact with both the urokinase receptor and the plasminogen activator inhibitor-1 (PAI-1) and the conserved cysteines of the NPP1 somatomedin B-like domain have been shown to mediate homodimerization. [4] As shown in the following schematic representation below the SMB domain contains eight Cys residues, arranged into four disulfide bonds. It has been suggested[ by whom?] that the active SMB domain may be permitted considerable disulfide bond heterogeneity or variability, provided that the Cys25-Cys31 disulfide bond is preserved. The three-dimensional structure of the SMB domain is extremely compact and the disulfide bonds are packed in the centre of the domain forming a covalently bonded core. [5] The structure of the SMB domain presents a new protein fold, with the only ordered secondary structure being a single-turn alpha-helix and a single-turn 3(10)-helix. [6]
xxCxxxxxxCxxxxxxxxxCxCxxxCxxxxxCCxxxxxCxxxxx ********************
'C': conserved cysteine probably involved in a disulfide bond. '*': position of the pattern.
ENPP1; ENPP2; ENPP3; PRG4; SUSD2; VTN;