Figure 2. Crystal structures of GFLV-F13 and GFLV-TD.

(A) The structures of GFLV-F13 and of GFLV-TD are very similar as illustrated by the extremely low r.m.s.d. values (see Table S1). For this reason only the highest resolution model (GFLV-TD) is represented in this figure. The ribbon diagram of the virus capsid is viewed down an icosahedral 2-fold axis normal to the plane of the paper. Sixty copies of the CP are arranged in an icosahedral pseudo T = 3 symmetry. The black line delineates one CP position. The grey pentagon, triangle and oval symbolize the icosahedral 5-fold, 3-fold and 2-fold symmetry axes, respectively. (B) Each CP comprises three jellyroll β sandwiches termed C, B and A domains from the N- to the C-terminus and are depicted in green, red and blue, respectively. A star indicates the position of residue 297. (C) The central section of the 2Fo-Fc electron density map (2 σ contour level) of a GFLV-F13 particle is viewed down a viral 2-fold axis. The outer radial dimensions along the icosahedral symmetry axes are indicated. (D) A thin slice of 2Fo-Fc electron density map (contoured at 1σ) reveals a strong density peak (about 3 σ in the 2Fo-Fc and 17 σ in the Fo-Fc map) on the 5-fold axis of GFLV-TD. The arrow symbolizing the axis points towards the outer surface of the particle as well as neighbouring charged residues (Lys⁴¹⁴ and Glu⁴¹¹) whereas Phe⁴¹² side chains are directed towards the viral cavity. The right panel shows a slightly shifted top view illustrating the organisation of the residues around the 5-fold axis. Five water molecules bridge Gly⁴¹³ carbonyl groups and Asp⁴¹¹ side chains to the large central ion, possibly a phosphate coming from the crystallization medium.