Mycobacterium tuberculosis copper‐regulated protein SocB is an intrinsically disordered protein that folds upon interaction with a synthetic phospholipid bilayer

Multiple genes in Mycobacterium tuberculosis (Mtb) are regulated by copper including socAB (s mall o rf induced by c opper A and B), which is induced by copper and repressed by RicR (r egulated i n c opper r epressor). socA and socB encode hypothetical proteins of 61 and 54 amino acids, respectively. Here, we use biophysical and computational methods to evaluate the SocB structure. We find that SocB lacks evidence for secondary structure, with no thermal cooperative unfolding event, according to circular dichroism measurements. 2D NMR spectra similarly exhibit hallmarks of a disordered structural state, which is also supported by analyzing SocB diffusion. Altogether, these findings suggest that by itself SocB is intrinsically disordered. Interestingly, SocB interacts with a synthetic phospholipid bilayer and becomes helical, which suggests that it may be membrane‐associated. Proteins 2016; 84:193–200. © 2015 Wiley Periodicals, Inc.