The TFE-induced transient native-like structure of the intrinsically disordered [Formula: see text] domain of Escherichia coli RNA polymerase

The transient folding of domain 4 of an E. coli RNA polymerase [Formula: see text] subunit ([Formula: see text] ) induced by an increasing concentration of 2,2,2-trifluoroethanol (TFE) in an aqueous solution was monitored by means of CD and heteronuclear NMR spectroscopy. NMR data, collected at a 30 % TFE, allowed the estimation of the population of a locally folded [Formula: see text] structure (CSI descriptors) and of local backbone dynamics ((15)N relaxation). The spontaneous organization of the helical regions of the initially unfolded protein into a TFE-induced 3D structure was revealed from structural constraints deduced from (15)N- to (13)C-edited NOESY spectra. In accordance with all the applied criteria, three highly populated α-helical regions, separated by much more flexible fragments, form a transient HLHTH motif resembling those found in PDB structures resolved for homologous proteins. All the data taken together demonstrate that TFE induces a transient native-like structure in the intrinsically disordered protein. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00249-014-0987-4) contains supplementary material, which is available to authorized users.