Somatomedin B, chordata (IPR020436)

Short name: Somatomedin_B_chordata

Overlapping homologous superfamilies


Domain relationships


Somatomedin B, 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 [PMID: 2447940]. Cys-rich somatomedin B-like domains are found in a number of proteins [PMID: 1710108], including plasma-cell membrane glycoprotein (which has nucleotide pyrophosphate and alkaline phosphodiesterase I activities) [PMID: 1647027] 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 homodimerisation [PMID: 12533192].

The SMB domain contains eight Cys residues, arranged into four disulphide bonds. It has been suggested that the active SMB domain may be permitted considerable disulphide bond heterogeneity or variability, provided that the Cys25-Cys31 disulphide bond is preserved. The three dimensional structure of the SMB domain is extremely compact and the disulphide bonds are packed in the centre of the domain forming a covalently bonded core [PMID: 15157085]. 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 [PMID: 12808446].

This entry is limited to Chordata proteins

GO terms

Biological Process

GO:0006955 immune response

Molecular Function

GO:0030247 polysaccharide binding
GO:0005044 scavenger receptor activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.