Fig. 4. Intra-pentamer and intra-hexamer interactions in HML2 CA^rec particles.

a, b Cartoon representations of a the T = 1 pentamer and b the D6 polar hexamer viewed along the five-fold and six-fold symmetry axes, respectively. The NTDs and CTDs are coloured as in Fig. 2. c Alignment of the NTDs from a T = 1 pentamer (pink) and a D6 “polar” hexamer (red). The central NTD is aligned and the arrows indicate the relative displacement of helices α1, α2 and α3 in adjacent monomers at the intra-pentamer or intra-hexamer interface. d NTD–CTD interactions in the T = 1 pentamer. e NTD domain superposition showing the relative displacement of the CTD in the T = 1 pentamer (pink/cyan) and the D6 “polar” hexamer (red/teal). f NTD–CTD interactions in the D6 polar hexamer. In d, f residues making interactions are shown as sticks, with hydrogen bonds shown as dashes, the prime (′) notation indicates the adjacent NTD and “mc” indicates a main-chain interaction. The conserved N-terminal P1 to α3–D67 interaction is also shown in each NTD for orientation.