Abstract
Cytochrome c oxidase (CcO) has four redox-active metal sites, Fe a , Fe a3 , CuA and CuB. Each site reversibly receives one electron equivalent. The four electron equivalents required to reduce the bound O2 are sequentially transferred from cytochrome c and each is coupled to the pumping of one proton equivalent. The purified enzyme fraction as prepared (the resting oxidized form) is not involved in catalytic turnover since one electron reduction of the resting oxidized form is not coupled to proton pumping. Redox and resonance Raman data suggest that a peroxide molecule bridges Fe a3 and CuB in the O2 reduction site. X-ray structural analyses show that the O-O bond length is 1.7 A, which is significantly longer than that of the typical peroxide bridge between two metals (1.5 A), suggesting an activated state of the bound peroxide. On the other hand, investigation of a bacterial CcO produced the proposal that the bound peroxide is not the intrinsic ligand; instead the peroxide is formed from hydroxyl radicals created by the strong X-ray radiation. Establishment of the ligand structure in the O2 reduction site is a prerequisite for elucidation of the proton-pumping mechanism.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
