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Ligand specificity and ligand‐induced conformational change in gal repressor
Author(s) -
Chatterjee Sumana,
Ghosh Kajari,
Dhar Amlanjyoti,
Roy Siddhartha
Publication year - 2002
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.10236
Subject(s) - galactose , repressor , chemistry , ligand (biochemistry) , lac repressor , operon , conformational change , biochemistry , stereochemistry , biophysics , receptor , biology , escherichia coli , gene , transcription factor
Gal repressor (GalR) binds D ‐galactose, which is responsible for lifting of repression of the gal operon. Proton T 1 measurements of α‐ and β‐anomers of galactose as a function of gal repressor show preferential binding of the β‐anomer. The β‐anomer was isolated by high‐performance liquid chromatography and was shown to bind tightly to GalR. Calorimetry was used to determine enthalpy changes at several temperatures. Heat capacity change was found to be positive, indicating that a significant amount of hydrophobic surface area was exposed upon galactose binding. Bis‐ANS binding to GalR is significantly enhanced in the presence of a saturating amount of galactose, indicating additional exposure of hydrophobic surfaces. We propose that the galactose‐induced conformational change involves the opening of the two subdomains, which may disrupt protein–protein interactions responsible for repression. Proteins 2002;49:554–559. © 2002 Wiley‐Liss, Inc.