Figure 3

Alteration of the UL18-binding site in LIR-2 D1. A. Structure of LIR-2 D1. The region of LIR-2 analogous to the proposed UL18-binding site in LIR-1. Main chain regions of the 76–84 F-G loop and Tyr 38, both of which implicated in LIR-1/UL18 interaction, are indicated in red. Side chains for LIR-2 residues 38 (Tyr), 76 (Gln), 80 (Arg) and 86 (Leu) are also shown. B. Conformation of Tyr 38 in LIR-1. Likely hydrogen bonds in (B) and (C) are shown as dotted lines. C. Conformation of Tyr 38 in LIR-2. The Ser (87) to Leu (86) change would cause a steric clash with the LIR-1 conformation of Tyr 38, and forces a side chain reorientation towards Gln 76. In LIR-1, substitution of Gln 76 for Tyr would similarly prevent adoption of the LIR-2 Tyr 38 orientation due to steric hindrance. D. Conformational shift of the 76–84 loop region. The LIR-1 loop (dark blue) protrudes from the side of the domain