Plasticity of proton pathway structure and water coordination in cytochrome c oxidase
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics2007 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 282, no 20, 15148-15158 p.Article in journal (Refereed) Published
Cytochrome c oxidase (CytcO) is a redox-driven, membrane-boundproton pump. One of the proton transfer pathways of the enzyme,the D pathway, used for the transfer of both substrate and pumpedprotons, accommodates a network of hydrogen-bonded water moleculesthat span the distance between an aspartate (Asp132), near theprotein surface, and glutamate Glu286, which is an internalproton donor to the catalytic site. To investigate how changesin the environment around Glu286 affect the mechanism of protontransfer through the pathway, we introduced a non-hydrogen-bonding(Ala) or an acidic residue (Asp) at position Ser197 (S197A orS197D), located 7 Å from Glu286. Although Ser197 is hydrogen-bondedto a water molecule that is part of the D pathway "proton wire,"replacement of the Ser by an Ala did not affect the proton transferrate. In contrast, the S197D mutant CytcO displayed a turnoveractivity of 35% of that of the wild-type CytcO, and the O2 reductionreaction was not linked to proton pumping. Instead, a fractionof the substrate protons was taken from the positive ("incorrect")side of the membrane. Furthermore, the pH dependence of theproton transfer rate was altered in the mutant CytcO. The resultsindicate that there is plasticity in the water coordinationof the proton pathway, but alteration of the electrostatic potentialwithin the pathway results in uncoupling of the proton translocationmachinery.
Place, publisher, year, edition, pages
2007. Vol. 282, no 20, 15148-15158 p.
IdentifiersURN: urn:nbn:se:su:diva-25431DOI: 10.1074/jbc.M700348200v1ISI: 000246589000054OAI: oai:DiVA.org:su-25431DiVA: diva2:199696