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Polar residues in the protein core of Escherichia coli thioredoxin are important for fold specificity

Bolon, Daniel N. and Mayo, Stephen L. (2001) Polar residues in the protein core of Escherichia coli thioredoxin are important for fold specificity. Biochemistry, 40 (34). pp. 10047-10053. ISSN 0006-2960. http://resolver.caltech.edu/CaltechAUTHORS:20110928-133003644

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Abstract

Most globular proteins contain a core of hydrophobic residues that are inaccessible to solvent in the folded state. In general, polar residues in the core are thermodynamically unfavorable except when they are able to form intramolecular hydrogen bonds. Compared to hydrophobic interactions, polar interactions are more directional in character and may aid in fold specificity. In a survey of 263 globular protein structures, we found a strong positive correlation between the number of polar residues at core positions and protein size. To probe the importance of buried polar residues, we experimentally tested the effects of hydrophobic mutations at the five polar core residues in Escherichia coli thioredoxin. Proteins with single hydrophobic mutations (D26I, C32A, C35A, T66L, and T77V) all have cooperative unfolding transitions like the wild type (wt), as determined by chemical denaturation. Relative to wt, D26I is more stable while the other point mutants are less stable. The combined 5-fold mutant protein (IAALV) is less stable than wt and has an unfolding transition that is substantially less cooperative than that of wt. NMR spectra as well as amide deuterium exchange indicate that IAALV is likely sampling a number of low-energy structures in the folded state, suggesting that polar residues in the core are important for specifying a well-folded native structure.


Item Type:Article
Related URLs:
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http://dx.doi.org/ 10.1021/bi010427y DOIUNSPECIFIED
http://pubs.acs.org/doi/abs/10.1021/bi010427yPublisherUNSPECIFIED
Additional Information:© 2001 American Chemical Society. Received March 1, 2001; Revised Manuscript Received June 5, 2001. Publication Date (Web): August 1, 2001. This research was supported by the Howard Hughes Medical Institute and the Ralph M. Parsons Foundation (S.L.M.), the Helen G. and Arthur McCallum Foundation, the Evelyn Sharp Graduate Fellowship, and Grant GM07616 from the National Institutes of Health (D.N.B.). We thank Scott Ross for guidance and assistance with NMR studies as well as useful discussions, and Arthur Street for compiling the data set analyzed in Figure 1.
Funders:
Funding AgencyGrant Number
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
Ralph M. Parsons FoundationUNSPECIFIED
Helen G. and Arthur McCallum FoundationUNSPECIFIED
Evelyn Sharp Graduate FellowshipUNSPECIFIED
NIHGM07616
Subject Keywords:Circular Dichroism; Mutagenesis: Site-Directed; Amino Acid Substitution; Amino Acid Sequence; Models: Molecular; Hydrogen Bonding; Escherichia coli; Thioredoxins; Nuclear Magnetic Resonance: Biomolecular; Protein Folding; Computer Simulation; Calorimetry: Differential Scanning; Protein Structure: Secondary; Recombinant Proteins; Spectrometry: Fluorescence
Record Number:CaltechAUTHORS:20110928-133003644
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20110928-133003644
Official Citation:Polar Residues in the Protein Core of Escherichia coli Thioredoxin Are Important for Fold Specificity† Daniel N. Bolon and and ,Stephen L. Mayo, Biochemistry 2001 40 (34), 10047-10053
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:25474
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 Oct 2011 18:44
Last Modified:26 Dec 2012 13:43

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