Protein Domain : Orbivirus inner capsid protein VP7 IPR001803

Type	Family
Description	Bluetongue virus is a representative of the Orbivirus genus of the Reoviridae [ ]. Orbiviruses infect mammalian hosts through insect vectors, causing economically-important diseases of domesticated animals []. They possess a segmented, double-stranded RNA genome within a capsid that comprises four major polypeptides, designated VP2, VP3, VP5 and VP7. On entering a target cell, an outer layer, formed from VP2 and VP5, is removed, leaving an intact core within the cell []. The core, which is 70nm across, contains 780 copies of VP7, which together form 260 trimeric 'bristly' capsomeres clothing an inner scaffold constructed from VP3 [].The 3D structure of VP7 reveals two domains, one a β-sandwich, the other a bundle of α-helices, and a short C-terminal arm, which is thought to unite trimers during capsid formation [ ]. A concentration of methionine residues at the core of the molecule could provide plasticity, relieving structural mismatches during assembly [].The 3D structure of baculovirus-expressed core protein VP7 of African horse sickness virus 4 (AHSV-4) has been determined to 2.3A resolution [ ]. During crystallisation, the two-domain protein is cleaved, leaving only the top domain, in a manner reminiscent of BTV VP7; this suggests that connections between top and bottom domains are relatively weak for these two distinct orbiviruses []. The top domains of both BTV and AHSV VP7 are trimeric and structurally very similar. Electron density maps indicate an extra density feature along their molecular 3-fold axes, probably the result of an unidentified ion []. The characteristics of the molecular surface indicate the possibility of attachment to the cell via attachment of an Arg-Gly-Asp (RGD) motif in the top domain of VP7 to a cellular integrin for both of these orbiviruses [].
Short Name	Orbi_VP7_capsid