Minor capsid proteins VP2 and VP3
| Minor capsid protein VP2 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | VP2 | ||||||||
| Pfam | PF00761 | ||||||||
| InterPro | IPR001070 | ||||||||
| |||||||||
Minor capsid protein VP2 and minor capsid protein VP3 are
icosahedral structures. The minor components are VP2 and VP3, which bind in the interior of the capsid.[1][2][3]
Gene expression
All three capsid proteins are expressed from
myristoylated.[1][3] Some members of the polyomavirus family, such as Merkel cell polyomavirus, do not appear to encode or express VP3, though VP2 is present.[3][5]
Structure and interactions
Both VP2 and VP3 are primarily
C-terminal ends.[7] Both VP2 and VP3 bind to the interior of VP1 pentamers in the assembled capsid.[1][2] It is generally believed that the stoichiometry of this interaction is one molecule of VP2 or VP3 to each VP1 pentamer,[2] though higher ratios have sometimes been reported, possibly indicating that pentamers can accommodate associations with two minor proteins.[3]
Function
VP2 and VP3 are thought to be involved in facilitating viral entry into the
JC virus both VP2 and VP3 seem to be essential for packaging the viral chromosome into the capsid,[12] while absence of these proteins in SV40 prevents successful entry into new host cells,[8][9] with variable effects on packaging reported.[8][13] In Merkel cell polyomavirus, the effect of VP2 appears to vary depending on the cell type of the infected cell.[3] In murine polyomavirus the minor proteins have been reported to induce apoptosis in the infected cell,[14] and in SV40 they have been identified as viroporins.[15]