Three-dimensional structure of human Rev1-CT domain (residues 1157-1251) determined by solution NMR spectroscopy. (A) Superposition of the backbone folds of 20 final lowest-energy structures obtained in CYANA followed by refinement in explicit solvent by CNS software. (B) Ribbon representation of Rev1-CT structure showing the positions of four α-helixes of the domain. Side chains are shown for residues that form core of the domain with less than 10% surface exposure and 10 Å2 accessible surface area (averaged over 20 best structures), including Leu 1159, Ala 1162 from the N-terminal β-hairpin, Val 1168, Leu 1172 (rev1-108), Ile 1176 (rev1-108) from α-helix H1, Val 1190 (rev1-110), Tyr 1193 (rev1-110), Cys 1194 (rev1-110), Leu 1197, Ile 1198 from α-helix H2, Leu 1206 (rev1-111), Val 1209 (rev1-111), Ile 1210 (rev1-111), Met 1213, Leu 1216, Met 1217 from α-helix H3, Trp 1225, Ala 1228, Ile 1232, Val 1236, Leu 1240 from α-helix H4; underlined are residues from four conserved 5-6 aa residue regions, referred to as rev1-108 to -111, identified by extensive sequence alignment of Rev1-CT domains from different eukaryotic species. (C) Electrostatic charge distribution on the surface of Rev1-CT domain (blue is positive, red is negative). Encircled is a pocket on the surface of the domain that accommodates FF residues of RIR motifs of Y-family polymerases.