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. 2012 Aug 22;7(8):e43871. doi: 10.1371/journal.pone.0043871

Figure 5. Two models for the outer shell facets of β-carboxysomes in S. elongatus PCC 7942.

Figure 5

A, a β-carboxysome facet model where the entire edge structure is formed from CcmO. B, a β-carboxysome facet where CcmO only occupies the EutS-like role. Two facets are shown with the top facet extending into the plane of the drawing at 138° from the bottom facet. Structural roles are: edge (CcmO, red), facet (CcmK2, grey), vertex (CcmL, brown) and niche (CcmK3, K4 and CcmP, Purple). The number of individual protein oligomers forming a single facet is listed below. The carboxysome edge length (90.2 nm) was calculated as the number of CcmK2 hexamers (CcmK2 hexamer edge length  = 35 Å [9]) sufficient to account for the facet-edge length (92.0 nm) calculated from the maximum cross-sectional diameter reported here (175±37 nm). The maximum cross-sectional diameter was assumed to represent the radius of a sphere circumscribing the icosahedral carboxysome.