Resolution of Stepwise Cooperativities of Copper Binding by the Homotetrameric Copper-Sensitive Operon Repressor (CsoR): Impact on Structure and Stability.
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 D2 -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).
Department of Chemistry, Indiana University, Bloomington, IN 47405-7102 (USA).
Alexander D
AD
Jacobs
Department of Chemistry, Indiana University, Bloomington, IN 47405-7102 (USA).
Feng-Ming James
FM
Chang
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210 (USA).
Lindsay
L
Morrison
Department of Chemistry, Indiana University, Bloomington, IN 47405-7102 (USA).
Jonathan M
JM
Dilger
Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210 (USA).
Vicki H
VH
Wysocki
Department of Chemistry, Indiana University, Bloomington, IN 47405-7102 (USA).
David E
DE
Clemmer
Department of Chemistry, Indiana University, Bloomington, IN 47405-7102 (USA). giedroc@indiana.edu.
David P
DP
Giedroc
D003300:Copper / Q000378:metabolism*; D056506:Geobacillus / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D009876:Operon; D011487:Protein Conformation; D055503:Protein Multimerization; D055550:Protein Stability; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*
D012097:Repressor Proteins; D003300:Copper
allostery; copper; metalloproteins; metalloregulation; surface-induced dissociation