title: Na(+)-induced reversal of the Ca2(+)-dependent red-shift of cytochrome a. Is there a hydronium output well in cytochrome c oxidase?
abstract: The Ca2(+)-induced red shift of the cytochrome a absorption spectrum is counteracted specifically by Na+ ions, whereas neither K+ nor Li+ do show comparable effect. At the same time Na+ does not reverse the H(+)-induced red shift of cytochrome a 2+. It is suggested that Na+ competes with Ca2+ for binding site(s) within the cytochrome oxidase output proton well communicating the heme a propionate substituent responsible for the Ca2(+)- or H(+)-induced red-shift of cytochrome a (Saari et al. 1980, J. Bioenerget. Biomembr. 12, 325-338) with the c-aqueous phase. The unusual ionic specificity of the well (Ca2+, Na+, proton) may point to H3O+ rather than H+ being the ion involved in proton conduction through the output well of cytochrome oxidase.
authors.affiliation: A.N. Belozersky Laboratory of Molecular Biology and Bioorganic Chemistry, Moscow State University, USSR.
authors.forename: H
authors.initials: H
authors.lastname: Mkrtchyan
authors.forename: T
authors.initials: T
authors.lastname: Vygodina
authors.forename: A
authors.initials: A
authors.lastname: Konstantinov
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D017936:Cytochrome a Group; D003580:Cytochromes / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology; D009861:Onium Compounds / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*; D013054:Spectrophotometry, Atomic
chemical_list: D017936:Cytochrome a Group; D003580:Cytochromes; D009861:Onium Compounds; C027727:hydronium ion; D006859:Hydrogen; D008094:Lithium; D012964:Sodium; D003576:Electron Transport Complex IV; D011188:Potassium; D002118:Calcium