REACTION OF MERCURIALS WITH THE CU-A CENTER IN THE SOLUBLE FRAGMENT OF CYTOCHROME BA(3) SUBUNIT-II FROM THERMUS-THERMOPHILUS

Optical absorption, EPR and electrospray ionization mass spectrometrie s were used to characterize a stoichiometric reaction between mercuria ls and the soluble ba(3)-Cu-A protein from Thermus thermophilus. Eithe r one Hg(II) or two RHg(II)ions react(s) to destroy the unique spectra l properties of the Cu-A center. EPR spectra of the resulting product indicate that one Cu from the binuclear Cu-A, center is released into the medium as a Type 2 Cu(II) while the other remains EPR silent, Mass spectra indicate that either one Hg(II) or two RHg(II) ions remain(s) bound to the protein along with one Cu, which is assumed to be a Cu(I ) ion. The latter is slowly released from the protein under aerobic co nditions as additional Type 2 Cu(II), and this process is catalyzed by fungal laccase, which serves as a strong one-electron oxidant.