Structure of Coenzyme A-Disulfide Reductase from Staphylococcus aureus at 1.54 A Resolution

摘要

Coenzyme A (CoASH) replaces glutathione as the major low molecular weight thiol in Staphylococcus aureus;it is maintained in the reduced state by coenzyme A-disulfide reductase (CoADR),a homodimeric enzyme similar to NADH peroxidase but containing a novel Cys43-SSCoA redox center.The crystal structure of S.aureus CoADR has been solved using multiwavelength anomalous dispersion data and refined at a resolution of 1.54 A.The resulting electron density maps define the Cys43-SSCoA disulfide conformation,with Cys43-S_(gamma) located at the flavin si face,3.2 A from FAD-C4aF,and the CoAS-moiety lying in an extended conformation within a cleft at the dimer interface.A well-ordered chloride ion is positioned adjacent to the Cys43-SSCoA disulfide and receives a hydrogen bond from Tyr361'-OH of the complementary subunit,suggesting a role for Tyr361' as an acid-base catalyst during the reduction of CoAS-disulfide.Tyr419'-OH is located 3.2 A from Tyr361'-OH as well and,based on its conservation in known functional CoADRs,also appears to be important for activity.Identification of residues involved in recognition of the CoAS-disulfide substrate and in formation and stabilization of the Cys43-SSCoA redox center has allowed development of a CoAS-binding motif.Bioinformatics analyses indicate that CoADR enzymes are broadly distributed in both bacterial and archaeal kingdoms,suggesting an even broader significance for the CoASH/CoAS-disulfide redox system in prokaryotic thiol/disulfide homeostasis.