Solution structure and dynamics of ADF/cofilin from Leishmania donovani

Abstract

Leishmania donovani ADF/cofilin (LdCof) is a novel member of ADF/cofilin family. LdCof depolymerizes, but does not co-sediment with, rabbit muscle actin filaments. Its F-actin depolymerizing activity is pH independent. Further, it possesses weak F-actin severing activity. In order to better understand its characteristic properties, we have determined the solution NMR structure of LdCof and have analyzed protein backbone dynamics from ¹⁵N-relaxation measurements. The structure of LdCof possesses a conserved ADF/cofilin fold with a central mixed β -sheet consisting of six β -strands which is surrounded by five α -helices. LdCof structure has conserved G/F-actin binding site which includes the characteristic long kinked α -helix (α 3). LdCof binds to rabbit muscle ADP-G-actin with 1:1 stoichiometry (K_d ~ 0.2 μ M). The F-actin binding site is not well formed and analysis of ¹⁵N-relaxation data shows that residues in the β 4-β 5 loop region and C-terminal are relatively flexible, which seems to be a determinant for the low F-actin severing activity of LdCof.