Thermodynamic Partitioning Model for Hydrophobic Binding of Polypeptides by GroEL: I. GroEL Recognizes the Signal Sequences of β-lactamase Precursor
From equilibrium measurements with urea we found a three-state thermodynamic and kinetic folding behavior for the precursor and mature form of Escherichia coli β-lactamase TEM2. The thermodynamic intermediate H of Escherichia coli β-lactamase and its precursor had no enzymatic activity, and a quench...
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Published in | Journal of molecular biology Vol. 242; no. 2; pp. 150 - 184 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
England
Elsevier Ltd
16.09.1994
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Subjects | |
Online Access | Get full text |
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Summary: | From equilibrium measurements with urea we found a three-state thermodynamic and kinetic folding behavior for the precursor and mature form of
Escherichia coli β-lactamase TEM2. The thermodynamic intermediate H of
Escherichia coli β-lactamase and its precursor had no enzymatic activity, and a quenched tryptophan fluorescence intensity, but a native-like wavelength of maximum intensity. State H of mature β-lactamase was 8·7 kcal mol-1 less stable than the native state N and about 4·2 kcal mol-1 more stable than the unfolded state U, extrapolated to absence of urea. In contrast, state H of precursor β-lactamase was even more stable than N by about 0·5 kcal mol-1 and about 6·9 kcal mol-1 more stable than U. Native pre-β-lactamase could be stabilized by lowering the pH value from 7·0 to 5·5, probably by protonating a histidine residue leading to an improved solubility of the signal sequence.
Synthetic peptides, containing 23 or 38 N-terminal amino-acid residues of pre-β-lactamase, were unable to compete with pre-β-lactamase for binding to GroEL. However, GroEL prevented the inactivation of mature β-lactamase by p38, consistent with competition between GroEL and mature β-lactamase for binding to p38. The equilibrium constant for dissociation
K
D of the complex between GroEL and p23, a peptide containing exclusively the signal sequence of pre-β-lactamase, was measured with the BIAcore™ instrument to be in the range 10-
7 to 10-
8 M. Our results are consistent with co-operative binding of GroEL to the mature part and to the signal sequence of pre-β-lactamase. We suggest a thermodynamic partitioning model for hydrophobic binding of polypeptides by GroEL. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 0022-2836 1089-8638 |
DOI: | 10.1006/jmbi.1994.1566 |