The H/D-exchange kinetics of the Escherichia coli co-chaperonin GroES studied by 2D NMR and DMSO-quenched exchange methods.

摘要: Abstract We studied hydrogen/deuterium-exchange reactions of peptide amide protons GroES using two different techniques: (1) two-dimensional 1 H– 15 N transverse-optimized NMR spectroscopy and (2) the dimethylsulfoxide-quenched hydrogen-exchange method combined with conventional heteronuclear single quantum coherence spectroscopy. By these techniques together direct experiments, we quantitatively evaluated exchange rates for 33 out 94 their protection factors, remaining 61 residues, obtained lower limits rates. The factors most highly protected were on order 10 6 –10 7 , values comparable in magnitude to those observed typical small globular proteins, but number a factor larger than was only 10, significantly smaller numbers reported indicating that significant portions free heptameric are flexible natively unfolded. amino acid residues 5 mainly located three β-strands form hydrophobic core GroES, while mobile loop (residues 17–34) not protected. orders value expected from equilibrium unfolding parameters previously reported, strongly suggesting is more complicated simple two-state or three-state mechanism may involve intermediate.