NDLI: Properties of Arg481 mutants of the aa 3-type cytochrome c oxidase from Rhodobacter sphaeroides suggest that neither R481 nor the nearby D-propionate of heme a 3 is likely to be the proton loading site of the proton pump

Content Provider	PubMed Central
Author	Lee, Hyun Ju Öjemyr, Linda Ahmet, Vakkasoglu Brzezinski, Peter Gennis, Robert B.
Abstract	Cytochrome c oxidase utilizes the energy from electron transfer and reduction of oxygen to water and pumps protons across the membrane, generating a proton motive force. A large body of biochemical work has shown that all the pumped protons enter the enzyme through the D-channel, which is apparent in X-ray structures as a chain of water molecules connecting D132 at the cytoplasmic surface of the enzyme, to E286, near the enzyme active site. The exit pathway utilized by pumped protons beyond this point and leading to the bacterial periplasm is not known. Also not known is the proton loading site (or sites) which undergoes changes in pKa in response to the chemistry at the enzyme active site and drives the proton pump mechanism. In this paper we examine the role of R481, a highly conserved arginine that forms an ion pair with the D-propionate of heme a3 . The R481H, R481N, R481Q and R481L mutants were examined. The R481H mutant oxidase is about 18% active and pumps protons with about 40% of the stoichiometry of the wild type. The R481N, R481Q and R481L mutants each retain only about 5% of the steady state activity, and this is shown to be due to inhibition of steps in the reaction of O2 with the reduced enzyme. Neither the R481N nor the R481Q mutant oxidases pump protons but, remarkably, the R481L mutant does pump protons with the same efficiency as the R481H mutant. Since the proton pump is clearly operating in the R481L mutant, these results rule out an essential role in the proton pump mechanism for R481 or its hydrogen bond partner, the D-propionate of heme a3 .
Related Links	http://dx.doi.org/10.1021/bi901015d
Ending Page	7131
Page Count	9
Starting Page	7123
File Format	PDF
ISSN	00062960
e-ISSN	15204995
Journal	Biochemistry
Issue Number	30
Volume Number	48
Language	English
Publisher Date	2009-08-04
Access Restriction	Open
Subject Keyword	Biochemistry Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Biochemistry

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Decoupling mutations in the D-channel of the aa 3-type cytochrome c oxidase from Rhodobacter sphaeroides suggest that a continuous hydrogen-bonded chain of waters is essential for proton pumping

Critical Structural Role of R481 in Cytochrome c Oxidase from Rhodobacter sphaeroides

Critical structural role of R481 in cytochrome c oxidase from Rhodobacter sphaeroides.

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Alternative initial proton acceptors for the D pathway of Rhodobacter sphaeroides cytochrome c oxidase

Replacing Asn207 by Aspartate at the Neck of the D Channel in the aa3-type Cytochrome c Oxidase from Rhodobacter sphaeroides Results in Decoupling the Proton Pump

Role of cooperative H+/e− Linkage (redox Bohr effect) at heme a/CuA and heme a 3/CuB in the proton pump of cytochrome c oxidase

Cytochrome aa3 of Rhodobacter sphaeroides as a model for mitochondrial cytochrome c oxidase. Purification, kinetics, proton pumping, and spectral analysis.

The proton collecting function of the inner surface of cytochrome c oxidase from Rhodobacter sphaeroides

Properties of Arg481 mutants of the aa 3-type cytochrome c oxidase from Rhodobacter sphaeroides suggest that neither R481 nor the nearby D-propionate of heme a 3 is likely to be the proton loading site of the proton pump

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