Figure 3. Interfaces in the asymmetric Vps4 hexamer.
Vps4 subunit pairs superimposed on the large AAA ATPase domain of the first subunit, as indicated. A-B, B-C and C-D interfaces are equivalent. The nucleotide-binding site is slightly expanded at the D-E interface due to a 15° relative rotation of subunit E. The E-F and F-A sites are open for nucleotide exchange. Inset (black rectangle), Close-up on the nucleotide binding site showing the nucleotide and coordinating P-loop for the first subunit, with the R288/R289-containing helix of the second subunits in color. These arginine finger Cα atoms shift by 2 Å at the D-E interface relative to the A-B, B-C, and C-D subunits. The E-F and F-A interfaces are shifted by 8 Å and 16 Å, respectively.