The intrinsically disordered Tarp protein from chlamydia binds actin with a partially preformed helix.

ABSTRACT: Tarp (translocated actin recruiting phosphoprotein) is an effector protein common to all chlamydial species that functions to remodel the host-actin cytoskeleton during the initial stage of infection. In C. trachomatis, direct binding to actin monomers has been broadly mapped to a 100-residue region (726-825) which is predicted to be predominantly disordered, with the exception of a ~10-residue ?-helical patch homologous to other WH2 actin-binding motifs. Biophysical investigations demonstrate that a Tarp726-825 construct behaves as a typical intrinsically disordered protein; within it, NMR relaxation measurements and chemical shift analysis identify the ten residue WH2-homologous region to exhibit partial ?-helix formation. Isothermal titration calorimetry experiments on the same construct in the presence of monomeric G-actin show a well defined binding event with a 1:1 stoichiometry and Kd of 102?nM, whilst synchrotron radiation circular dichroism spectroscopy suggests the binding is concomitant with an increase in helical secondary structure. Furthermore, NMR experiments in the presence of G-actin indicate this interaction affects the proposed WH2-like ?-helical region, supporting results from in silico docking calculations which suggest that, when folded, this ?-helix binds within the actin hydrophobic cleft as seen for other actin-associated proteins.

SUBMITTER: Tolchard J 

PROVIDER: S-EPMC5792643 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature