NMR analysis of partially folded states and persistent structure in the alpha subunit of tryptophan synthase: implications for the equilibrium folding mechanism of a 29-kDa TIM barrel protein.

ABSTRACT: Structural insights into the equilibrium folding mechanism of the alpha subunit of tryptophan synthase (alpha TS) from Escherichia coli, a (beta alpha)(8) TIM barrel protein, were obtained with a pair of complementary nuclear magnetic resonance (NMR) spectroscopic techniques. The secondary structures of rare high-energy partially folded states were probed by native-state hydrogen-exchange NMR analysis of main-chain amide hydrogens. 2D heteronuclear single quantum coherence NMR analysis of several (15)N-labeled nonpolar amino acids was used to probe the side chains involved in stabilizing a highly denatured intermediate that is devoid of secondary structure. The dynamic broadening of a subset of isoleucine and leucine side chains and the absence of protection against exchange showed that th

SUBMITTER: Vadrevu R 

PROVIDER: S-EPMC2310134 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature