1c8d
From Proteopedia
CANINE PANLEUKOPENIA VIRUS EMPTY CAPSID STRUCTURE
Structural highlights
Function[CAPSD_PAVCD] Capsid protein self-assembles to form an icosahedral capsid with a T=1 symmetry, about 22 nm in diameter, and consisting of 60 copies of two size variants of the capsid proteins, VP1 and VP2, which differ by the presence of an N-terminal extension in the minor protein VP1. The capsid encapsulates the genomic ssDNA. Capsid proteins are responsible for the attachment to host cell receptor TFRC. This attachment induces virion internalization predominantly through clathrin-endocytosis. Binding to the host receptors also induces capsid rearrangements leading to surface exposure of VP1 N-terminus, specifically its phospholipase A2-like region and nuclear localization signal(s). VP1 N-terminus might serve as a lipolytic enzyme to breach the endosomal membrane during entry into host cell (By similarity). Intracytoplasmic transport involves microtubules and interaction between capsid proteins and host dynein. Exposure of nuclear localization signal probably allows nuclear import of capsids.[1] [2] [3] 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 PubMedCanine parvovirus (CPV) emerged in 1978 as a host range variant of feline panleukopenia virus (FPV). This change of host was mediated by the mutation of five residues on the surface of the capsid. CPV and FPV enter cells by endocytosis and can be taken up by many non-permissive cell lines, showing that their host range and tissue specificity are largely determined by events occurring after cell entry.We have determined the structures of a variety of strains of CPV and FPV at various pH values and in the presence or absence of Ca(2+). The largest structural difference was found to occur in a flexible surface loop, consisting of residues 359 to 375 of the capsid protein. This loop binds a divalent calcium ion in FPV and is adjacent to a double Ca(2+)-binding site, both in CPV and FPV. Residues within the loop and those associated with the double Ca(2+)-binding site were found to be essential for virus infectivity. The residues involved in the double Ca(2+)-binding site are conserved only in FPV and CPV.Our results show that the loop conformation and the associated Ca(2+)-binding are influenced by the Ca(2+) concentration, as well as pH. These changes are correlated with the ability of the virus to hemagglutinate erythrocytes. The co-localization of hemagglutinating activity and host range determinants on the virus surface implies that these properties may be functionally linked. We speculate that the flexible loop and surrounding regions are involved in binding an as yet unidentified host molecule and that this interaction influences host range. Host range and variability of calcium binding by surface loops in the capsids of canine and feline parvoviruses.,Simpson AA, Chandrasekar V, Hebert B, Sullivan GM, Rossmann MG, Parrish CR J Mol Biol. 2000 Jul 14;300(3):597-610. PMID:10884355[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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