Direct detection of formate ligation in cytochrome c oxidase by ATR-FTIR spectroscopy.
The IR signature of binding of formate to the heme a(3-)Cu(B) binuclear site of bovine cytochrome c oxidase has been obtained by perfusion ATR-FTIR spectroscopy. The data show unequivocally that formate binds in its anionic form despite its binding being electroneutral overall. The bound formate can be distinguished from free ligand by the binding-induced sharpening and downshifting of vibrational bands. Formate ligation also causes shifts of vibrational modes of heme a(3) and its substituents and perturbation of histidine residues. The association of the accompanying protonation change with a carboxylate or tyrosine can be ruled out and may involve a histidine metal ligand or, more likely, a simple displacement into the bulk phase of a hydroxide ligand to heme a(3) or CU(B), a reaction which would account for stoichiometric proton uptake and maintenance of net charge within the binuclear center domain.
The Glynn Laboratory of Bioenergetics, Department of Biology, University College London, Gower Street, London WC1E 6BT, UK.
Masayo
M
Iwaki
Peter R
PR
Rich
D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D005561:Formates / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D013053:Spectrophotometry / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
D005561:Formates; C030544:formic acid; C027728:heme a; D006418:Heme; D003576:Electron Transport Complex IV