title: Time-resolved OH-->EH transition of the aberrant ba3 oxidase from Thermus thermophilus.
abstract: The kinetics of single-electron injection into the oxidized nonrelaxed state (OH --> EH transition) of the aberrant ba3 cytochrome oxidase from Thermus thermophilus, noted for its lowered efficiency of proton pumping, was investigated by time-resolved optical spectroscopy. Two main phases of intraprotein electron transfer were resolved. The first component (tau approximately 17 mus) reflects oxidation of CuA and reduction of the heme groups (low-spin heme b and high-spin heme a3 in a ratio close to 50:50). The subsequent component (tau 420 mus) includes reoxidation of both hemes by CuB. This is in significant contrast to the OH--> EH transition of the aa3-type cytochrome oxidase from Paracoccus denitrificans, where the fastest phase is exclusively due to transient reduction of the low-spin heme a, without electron equilibration with the binuclear center. On the other hand, the one-electron reduction of the relaxed O state in ba3 oxidase was similar to that in aa3 oxidase and only included rapid electron transfer from CuA to the low-spin heme b. This indicates a functional difference between the relaxed O and the pulsed OH forms also in the ba3 oxidase from T. thermophilus.
authors.affiliation: Department of Molecular Energetics of Microorganisms, Lomonosov Moscow State University, Moscow, Russian Federation.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Siletsky
authors.forename: Ilya
authors.initials: I
authors.lastname: Belevich
authors.forename: Mårten
authors.initials: M
authors.lastname: Wikström
authors.forename: Tewfik
authors.initials: T
authors.lastname: Soulimane
authors.forename: Michael I
authors.initials: MI
authors.lastname: Verkhovsky
mesh_terms: D002384:Catalysis; D003573:Cytochrome b Group / Q000737:chemistry* / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000737:chemistry*; D006878:Hydroxides / Q000737:chemistry*; D007700:Kinetics; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D003573:Cytochrome b Group; D006878:Hydroxides; D006418:Heme; C031356:hydroxide ion; C058557:cytochrome ba3; D003576:Electron Transport Complex IV