Crystal structure of human V‐1 in the apo form.

V‐1, also known as myotrophin, is a 13 kDa ankyrin‐repeat protein that binds and inhibits the heterodimeric actin capping protein (CP), which is a key regulator of cytoskeletal actin dynamics. The crystal structure of V‐1 in complex with CP revealed that V‐1 recognizes CP via residues spanning several ankyrin repeats. Here, the crystal structure of human V‐1 is reported in the absence of the specific ligand at 2.3 Å resolution. In the asymmetric unit, the crystal contains two V‐1 monomers that exhibit nearly identical structures (Cα r.m.s.d. of 0.47 Å). The overall structures of the two apo V‐1 chains are also highly similar to that of CP‐bound V‐1 (Cα r.m.s.d.s of <0.50 Å), indicating that CP does not induce a large conformational change in V‐1. Detailed structural comparisons using the computational program All Atom Motion Tree revealed that CP binding can be accomplished by minor side‐chain rearrangements of several residues. These findings are consistent with the known biological role of V‐1, in which it globally inhibits CP in the cytoplasm. [ABSTRACT FROM AUTHOR]