Exploring the Energy Surface of Protein Folding by Structure-Reactivity Relationships and Engineered Proteins: Observation of Ftammond Behavior for the Gross Structure of the Transition State and Anti-Hammond Behavior for Structural Elements for Unfolding/Folding of Bamase. Matthews, J. & Fersht, A. Biochemistry, 34(20):6805-6814, 1995. cited By 125
Exploring the Energy Surface of Protein Folding by Structure-Reactivity Relationships and Engineered Proteins: Observation of Ftammond Behavior for the Gross Structure of the Transition State and Anti-Hammond Behavior for Structural Elements for Unfolding/Folding of Bamase [link]Paper  doi  abstract   bibtex   
The structure of α-helix1 (residues 6-18) in the transition state for the unfolding of bamase has been previously characterized by comparing the kinetics and thermodynamics of folding of wild-type protein with those of mutants whose side chains have been cut back, in the main, to that of alanine. The structure of the transition state has now been explored further by comparing the kinetics and thermodynamics of folding of glycine mutants with those of the alanine mutants at solvent-exposed positions in the α-helices of bamase. Such “Ala→Gly scanning” provides a general procedure for examining the structure of solventexposed regions in the transition state. A gradual change of structure of the transition state was detected as helix1 becomes increasingly destabilized on mutation. The extent of change of stmcture of helix1 in the transition state for the mutant proteins was probed by a further round of Ala→Gly scanning of those mutants. Destabilization of the helix1 was found to cause the overall transition state for unfolding to become closer in stmcture to that of the folded protein. This is analogous to the conventional Hammond effect in physical-organic chemistry whereby the transition state moves parallel to the reaction coordinate with change in stmcture. But, paradoxically, the stmcture of helix1 itself becomes less folded in the transition state as helix1 becomes destabilized. This is analogous, however, to the rarer anti-Hammond effect in which there is movement perpendicular to the reaction coordinate. These observations are rationalized by plotting correlation diagrams of degree of formation of individual elements of stmcture against the degree of formation of overall stmcture in the transition state. There is a relatively smooth movement of the degree of compactness in the transition state against changes in activation energy on mutation that suggests a smooth movement of the transition state along the energy surface on mutation rather than a switch between two different parallel pathways. The results are consistent with the transition state having closely spaced energy levels. Helix1, which appears to be an initiation point and forms early in the folding of wild-type protein, may be radically destabilized to the extent that it forms late in the folding of mutants. The order of events in folding may thus not be cmcial. © 1995, American Chemical Society. All rights reserved.
@ARTICLE{Matthews19956805,
author={Matthews, J.M. and Fersht, A.R.},
title={Exploring the Energy Surface of Protein Folding by Structure-Reactivity Relationships and Engineered Proteins: Observation of Ftammond Behavior for the Gross Structure of the Transition State and Anti-Hammond Behavior for Structural Elements for Unfolding/Folding of Bamase},
journal={Biochemistry},
year={1995},
volume={34},
number={20},
pages={6805-6814},
doi={10.1021/bi00020a027},
note={cited By 125},
url={https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029041315&doi=10.1021%2fbi00020a027&partnerID=40&md5=75ca73d12825c1a02d81101b017f2470},
affiliation={MRC Unit for Protein Function and Design, Cambridge Centre for Protein Engineering, University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW, U.K., United Kingdom},
abstract={The structure of α-helix1 (residues 6-18) in the transition state for the unfolding of bamase has been previously characterized by comparing the kinetics and thermodynamics of folding of wild-type protein with those of mutants whose side chains have been cut back, in the main, to that of alanine. The structure of the transition state has now been explored further by comparing the kinetics and thermodynamics of folding of glycine mutants with those of the alanine mutants at solvent-exposed positions in the α-helices of bamase. Such “Ala→Gly scanning” provides a general procedure for examining the structure of solventexposed regions in the transition state. A gradual change of structure of the transition state was detected as helix1 becomes increasingly destabilized on mutation. The extent of change of stmcture of helix1 in the transition state for the mutant proteins was probed by a further round of Ala→Gly scanning of those mutants. Destabilization of the helix1 was found to cause the overall transition state for unfolding to become closer in stmcture to that of the folded protein. This is analogous to the conventional Hammond effect in physical-organic chemistry whereby the transition state moves parallel to the reaction coordinate with change in stmcture. But, paradoxically, the stmcture of helix1 itself becomes less folded in the transition state as helix1 becomes destabilized. This is analogous, however, to the rarer anti-Hammond effect in which there is movement perpendicular to the reaction coordinate. These observations are rationalized by plotting correlation diagrams of degree of formation of individual elements of stmcture against the degree of formation of overall stmcture in the transition state. There is a relatively smooth movement of the degree of compactness in the transition state against changes in activation energy on mutation that suggests a smooth movement of the transition state along the energy surface on mutation rather than a switch between two different parallel pathways. The results are consistent with the transition state having closely spaced energy levels. Helix1, which appears to be an initiation point and forms early in the folding of wild-type protein, may be radically destabilized to the extent that it forms late in the folding of mutants. The order of events in folding may thus not be cmcial. © 1995, American Chemical Society. All rights reserved.},
keywords={alanine;  glycine;  ribonuclease, amino acid substitution;  article;  conformational transition;  enzyme stability;  mutation;  nonhuman;  priority journal;  protein folding;  structure activity relation;  thermodynamics, Alanine;  Base Sequence;  Glycine;  Hydrogen Bonding;  Kinetics;  Molecular Sequence Data;  Mutagenesis;  Protein Denaturation;  Protein Engineering;  Protein Folding;  Protein Structure, Secondary;  Ribonucleases;  Structure-Activity Relationship;  Support, Non-U.S. Gov't;  Thermodynamics},
correspondence_address1={Matthews, J.M.; Joint Protein Structure Laboratory, , Victoria 3050, Australia},
issn={00062960},
pubmed_id={7756312},
language={English},
abbrev_source_title={Biochemistry},
document_type={Article},
source={Scopus},
}
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