Structural basis of molecular recognition between ESCRT-III-like protein Vps60 and AAA-ATPase regulator Vta1 in the multivesicular body pathway.

The AAA-ATPase Vps4 is critical for function of the multivesicular body sorting pathway, which impacts cellular phenomena ranging from receptor down-regulation to viral budding to cytokinesis. Vps4 activity is stimulated by the interaction between Vta1 and Vps60, but the structural basis for this interaction is unclear. The fragment Vps60(128-186) was reported to display the full activity of Vps60. Vta1 interacts with Vps60 using its N-terminal domain (Vta1NTD). In this work, the structure of Vps60(128-186) in complex with Vta1NTD was determined using NMR techniques, demonstrating a novel recognition mode of the microtubule-interacting and transport (MIT) domain in which Vps60(128-186) interacts with Vta1NTD through helices α4' and α5', extending over Vta1NTD MIT2 domain helices 1-3. The Vps60 binding does not result in Vta1 conformational changes, further revealing the fact that Vps4 ATPase is enhanced by the interaction between Vta1 and Vps60 in an unanticipated manner.