The tfe-induced transient native-like structure of the intrinsically disordered (Formula presented) domain of escherichia coli rna polymerase

Abstract

The transient folding of domain 4 of an E. coli RNA polymerase (Formula presented.) subunit (Formula presented.) induced by an increasing concentration of 2,2,2-trifuoroethanol (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 presents) structure (CSI descriptors) and of local backbone dynamics (15N 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 from15N- to13C-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.