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. Author manuscript; available in PMC: 2014 Aug 6.
Published in final edited form as: Structure. 2013 Jul 25;21(8):1374–1383. doi: 10.1016/j.str.2013.06.007

Figure 5.

Figure 5

Procapsid expansion. (A) CryoEM reconstructions of three conformational states of the ϕ6 capsid at 16 Å resolution. (B, C) Models of a portion of capsid comprising a pentamer of P1A subunits (blue, green) and surrounding P1B subunits (red, yellow) subunits, viewed from above (B) and from the side (C). Expansion to intermediate 1 is the major transition of the maturing capsid, achieved by rotation of P1B subunits around an axis connecting the 3-fold icosahedral axes (bar in panel A). This rotation appears to stabilize the P1B/P1B interface at the 2-fold axis (Figure 6) and seals gaps between P1A and P1B subunits near the 3-fold axis (arrow). Further expansion to intermediate 2 is achieved by outward movement of the P1A subunits. The final step to the nucleocapsid state is accompanied by local conformational changes in the P1A subunits that correlate with increased outward curvature at the 5-fold axis. Scale bar: 100 Å. See also Movie S3.