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Fig. 1. Structures of the SV40 virion, SV40 VP1-pentamer, and sialy-
loligosaccharide receptor fragments binding to murine polyomavirus VP1-
pentamer. ( A )C-
backbone drawing of SV40 virion reconstructed from
the structural unit of the SV40 VP1 capsid (1SVA) using VIPER. ( B ) Each
SV40 VP1 protein in one VP1-pentamer is highlighted with different colors.
( C ) sialyloligosaccharide receptor fragments binding to murine polyomavirus
VP1-pentamer (1SID) are highlighted with red.
α
different symmetry locations on the particle with intrinsic activity of
the VP1. The capsid of SV40 also contains two internal proteins, VP2
and VP3, where VP3 is an amino terminally truncated form of VP2
(Fig. 3). Low resolution (25 Å ) crystallographic studies of polyoma
have shown that a part of VP2/3 inserts into the inward-facing cavity
along the 5-fold axis of a VP1-pentamer. 5 In vitro binding studies have
confirmed that the VP1-pentamer interacts tightly with VP2/3; that a
sequence near the common C-terminus of VP2/3 is necessary and
sufficient for complex formation 6 ; and that VP3 residues 155 to 190
bind to VP1-pentamers. 7 Thus, the C-terminus of VP2/3 polypeptide
chain binds in one of five equally probable orientations to its pentameric
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