Reduction of cysteine sulfinic acid in peroxiredoxin by sulfiredoxin proceeds directly through a sulfinic phosphoryl ester intermediate.
Sulfiredoxin (Srx) catalyzes a novel enzymatic reaction, the reduction of protein cysteine sulfinic acid, Cys-SO(2)(-). This reaction is unique to the typical 2-Cys peroxiredoxins (Prx) and plays a role in peroxide-mediated signaling by regulating the activity of Prxs. Two mechanistic schemes have been proposed that differ regarding the first step of the reaction. This step involves either the direct transfer of the gamma-phosphate of ATP to the Prx molecule or through Srx acting as a phosphorylated intermediary. In an effort to clarify this step of the Srx reaction, we have determined the 1.8A resolution crystal structure of Srx in complex with ATP and Mg(2+). This structure reveals the role of the Mg(2+) ion to position the gamma-phosphate toward solvent, thus preventing an in-line attack by the catalytic residue Cys-99 of Srx. A model of the quaternary complex is consistent with this proposal. Furthermore, phosphorylation studies on several site-directed mutants of Srx and Prx, including the Prx-Asp mimic of the Prx-SO(2)(-) species, support a mechanism where phosphorylation of Prx-SO(2)(-) is the first chemical step.
Jönsson
Thomas J
TJ
Center for Structural Biology and Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
Murray
Michael S
MS
Johnson
Lynnette C
LC
Lowther
W Todd
WT
D000255:Adenosine Triphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019943:Amino Acid Substitution; D020134:Catalytic Domain / Q000502:physiology; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050862:Oxidoreductases Acting on Sulfur Group Donors; D054464:Peroxiredoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology
D000255:Adenosine Triphosphate; D010088:Oxidoreductases; D054464:Peroxiredoxins; D050862:Oxidoreductases Acting on Sulfur Group Donors; C504024:SRXN1 protein, human; D003545:Cysteine; C013461:cysteine sulfinic acid