The CymR regulator in complex with the enzyme CysK controls cysteine metabolism in Bacillus subtilis.
Several enzymes have evolved as sensors in signal transduction pathways to control gene expression, thereby allowing bacteria to adapt efficiently to environmental changes. We recently identified the master regulator of cysteine metabolism in Bacillus subtilis, CymR, which belongs to the poorly characterized Rrf2 family of regulators. We now report that the signal transduction mechanism controlling CymR activity in response to cysteine availability involves the formation of a stable complex with CysK, a key enzyme for cysteine biosynthesis. We carried out a comprehensive quantitative characterization of this regulator-enzyme interaction by surface plasmon resonance and analytical ultracentrifugation. We also showed that O-acetylserine plays a dual role as a substrate of CysK and as an effector modulating the CymR-CysK complex formation. The ability of B. subtilis CysK to bind to CymR appears to be correlated to the loss of its capacity to form a cysteine synthase complex with CysE. We propose an original model, supported by the determination of the intracellular concentrations of the different partners, by which CysK positively regulates CymR in sensing the bacterial cysteine pool.
Tanous
Catherine
C
Institut Pasteur, UnitédeGénétique des Génomes Bactériens, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, 75724 Paris cedex 15, France.
Soutourina
Olga
O
Raynal
Bertrand
B
Hullo
Marie-Françoise
MF
Mervelet
Peggy
P
Gilles
Anne-Marie
AM
Noirot
Philippe
P
Danchin
Antoine
A
England
Patrick
P
Martin-Verstraete
Isabelle
I
D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003545:Cysteine / Q000096:biosynthesis* / Q000235:genetics; D003547:Cysteine Synthase / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D020349:Surface Plasmon Resonance / Q000379:methods
D001426:Bacterial Proteins; D009097:Multienzyme Complexes; D003547:Cysteine Synthase; D003545:Cysteine