PMID:11841204

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Citation

Rodriguez, HM, Robertson, AD and Gregoret, LM (2002) Native state EX2 and EX1 hydrogen exchange of Escherichia coli CspA, a small beta-sheet protein. Biochemistry 41:2140-8

Abstract

Escherichia coli CspA is a small all-beta-sheet protein that folds fast (tau = 4 ms) via an apparent two-state mechanism. Our previous studies have shown that a large aromatic cluster on the surface of the protein participates in the rate-limiting step of folding and thus may be part of the folding nucleus of this protein. To obtain a more detailed picture of molecular events at the peptide backbone during unfolding and folding of CspA, we used native state hydrogen exchange and nuclear magnetic resonance spectroscopy (NMR). The experiments with native CspA were performed over a range of pH values from low pH, where exchange is governed by a rapid equilibrium before chemical exchange (EX2 exchange), to high pH, where exchange is dictated by the rate of unfolding (EX1 exchange). Rates of folding and unfolding were determined for 11 residues. The distribution of rates of folding within the structure of CspA suggests that hairpin turns, including one near the aromatic cluster, may nucleate the folding of CspA.

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Keywords

Amides/chemistry; Bacterial Proteins/chemistry; Computer Simulation; Escherichia coli/chemistry; Hot Temperature; Hydrogen-Ion Concentration; Kinetics; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular; Protein Folding; Protein Structure, Secondary; Protons; RNA-Binding Proteins/chemistry; Thermodynamics

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