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Resolution of Stepwise Cooperativities of Copper Binding by the Homotetrameric Copper‐Sensitive Operon Repressor (CsoR): Impact on Structure and Stability
Author(s) -
Jacobs Alexander D.,
Chang FengMing James,
Morrison Lindsay,
Dilger Jonathan M.,
Wysocki Vicki H.,
Clemmer David E.,
Giedroc David P.
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201506349
Subject(s) - cooperativity , tetramer , allosteric regulation , operon , cooperative binding , chemistry , repressor , biophysics , plasma protein binding , crystallography , binding site , biochemistry , biology , receptor , enzyme , escherichia coli , transcription factor , gene
The cooperativity of ligand binding is central to biological regulation and new approaches are needed to quantify these allosteric relationships. Herein, we exploit a suite of mass spectrometry (MS) experiments to provide novel insights into homotropic Cu‐binding cooperativity, gas‐phase stabilities and conformational ensembles of the D 2 ‐symmetric, homotetrameric copper‐sensitive operon repressor (CsoR) as a function of Cu I ligation state. Cu I binding is overall positively cooperative, but is characterized by distinct ligation state‐specific cooperativities. Structural transitions occur upon binding the first and fourth Cu I , with the latter occurring with significantly higher cooperativity than previous steps; this results in the formation of a holo‐tetramer that is markedly more resistant than apo‐, and partially ligated CsoR tetramers toward surface‐induced dissociation (SID).