Figure 2. Representation of MeV H head domains complexed with soluble Slam receptor based on the coordinates reported by Hashiguchi and colleagues [31].

Slam moieties (dark green) and covalently linked H dimers (cyan and light purple) in the tetrameric arrangement are highlighted. Receptor binding is proposed to trigger a significant reorganization of the non-covalent dimer-dimer interface (form I versus form II [31]). In the original X-ray analysis, form II was observed when an additional L482R mutation was introduced into MeV H. This mutation was found to enhance SLAM-dependent fusion and also appeared in a clinical MeV isolate of the D1 genotype [31]. Structural renderings were prepared as described for Figure 1. Dotted lines highlight the dimer–dimer intersection. Hypothetical positions of the H stalk domains are marked in the side view representations.