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. Author manuscript; available in PMC: 2022 Apr 27.
Published in final edited form as: Nat Struct Mol Biol. 2022 Jan 10;29(1):47–58. doi: 10.1038/s41594-021-00706-2

Fig. 5 |. IMPDH1 retinal variant (595) constrains filament architecture.

Fig. 5 |

a, Low-pass filtered cryo-EM reconstruction of the IMPDH1(595) extended filament (bound to ATP) and compressed filament (bound to GTP, ATP, IMP, NAD+). b–k, Compressed IMPDH1(595) filament (bound to GTP, ATP, IMP, NAD+). b, Interface-focused cryo-EM filament reconstruction. Eight monomers are colored with catalytic domain (green), regulatory domain (pink) and variant helix (yellow). c, View of the top of an octamer from inside the filament. Surface representation of the atomic model at the assembly interface, with buried residues in cyan. d, Additional n-terminal helix residues −18 to −7 in yellow in density. e, Surface representation of interface with one monomer in ribbon (light green). Additional n-terminal helix in yellow. The monomer it contacts across the octamer interface is colored dark green/pink with residues the ribbon monomer contacts in aqua. Tyr12 is shown in orange spheres. f, Close-up view of the interface contacts. g, Surface representation of interface with one monomer in ribbon (light green). Additional n-terminal helix in yellow. The neighbor monomer in the tetramer is colored green with residues the ribbon monomer contacts in aqua. Y12 is shown in orange spheres. h, Close-up view of the new n-terminal helix contacts with the adjacent monomer in the tetramer. i, Comparison of the catalytic tetramers of inhibited IMPDH1(514) GTP/IMP/NAD+ (dark green) to inhibited IMPDH1(595) GTP/ATP/IMP/NAD+ (light green). Aligned on monomers with an asterisk.