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

Tsuyoshi Egawa, Hyun Ju Lee, Robert B. Gennis, Syun-Ru Yeh, Denis L. Rousseau

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

The R481 residue in cytochrome c oxidase from Rhodobacter sphaeroides forms hydrogen bonds with the propionate groups of both heme a and heme a3. It has been postulated that R481 is the proton loading site in the proton exit pathway essential for proton translocation. A recent functional study showed that the mutations of R481 to His, Leu and Gln cause the reduction of the activity to ∼ 5-18% of the native level, and the absence of proton pumping in R481Q but retention of ∼ 40% efficiency in R481H and R481L (H.J. Lee, L. Öjemyr, A. Vakkasoglu, P. Brzezinski and R. B. Gennis, manuscript submitted). To decipher the molecular mechanism underlying the perturbed functionalities, we have used resonance Raman spectroscopy to examine the structural properties of the three mutants. The data show that the frequencies of the formyl C{double bond, short} O stretching modes of both the heme a and a3 in the mutants are characteristic of formyl groups exposed to an aqueous environment, indicating that the mutations disrupt the native H-bonding interaction between the formyl group of heme a and R52, as well as the hydrophobic environment surrounding the formyl group of heme a3. In addition to the change in the environments of heme a and a3, the Raman data show that the mutations induce a partial conversion of the heme a3 from a high-spin to a low-spin state, suggesting that the mutations are associated with the rearrangement of the CuB-heme a3 binuclear center. The Raman results reported here demonstrate that R481 plays a critical role in supporting efficient proton pumping, by holding the heme groups in a proper environment.

Original languageEnglish (US)
Pages (from-to)1272-1275
Number of pages4
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1787
Issue number10
DOIs
StatePublished - Oct 2009

Fingerprint

Rhodobacter sphaeroides
Electron Transport Complex IV
Protons
Mutation
mannosulfan
heme a
Manuscripts
Raman Spectrum Analysis
Propionates
Heme
Stretching
Raman spectroscopy
Structural properties
Hydrogen
Hydrogen bonds

Keywords

  • Bioenergetics
  • Heme
  • Mutants
  • Proton translocation
  • Raman scattering

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Cell Biology

Cite this

Critical structural role of R481 in cytochrome c oxidase from Rhodobacter sphaeroides. / Egawa, Tsuyoshi; Lee, Hyun Ju; Gennis, Robert B.; Yeh, Syun-Ru; Rousseau, Denis L.

In: Biochimica et Biophysica Acta - Bioenergetics, Vol. 1787, No. 10, 10.2009, p. 1272-1275.

Research output: Contribution to journalArticle

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abstract = "The R481 residue in cytochrome c oxidase from Rhodobacter sphaeroides forms hydrogen bonds with the propionate groups of both heme a and heme a3. It has been postulated that R481 is the proton loading site in the proton exit pathway essential for proton translocation. A recent functional study showed that the mutations of R481 to His, Leu and Gln cause the reduction of the activity to ∼ 5-18{\%} of the native level, and the absence of proton pumping in R481Q but retention of ∼ 40{\%} efficiency in R481H and R481L (H.J. Lee, L. {\"O}jemyr, A. Vakkasoglu, P. Brzezinski and R. B. Gennis, manuscript submitted). To decipher the molecular mechanism underlying the perturbed functionalities, we have used resonance Raman spectroscopy to examine the structural properties of the three mutants. The data show that the frequencies of the formyl C{double bond, short} O stretching modes of both the heme a and a3 in the mutants are characteristic of formyl groups exposed to an aqueous environment, indicating that the mutations disrupt the native H-bonding interaction between the formyl group of heme a and R52, as well as the hydrophobic environment surrounding the formyl group of heme a3. In addition to the change in the environments of heme a and a3, the Raman data show that the mutations induce a partial conversion of the heme a3 from a high-spin to a low-spin state, suggesting that the mutations are associated with the rearrangement of the CuB-heme a3 binuclear center. The Raman results reported here demonstrate that R481 plays a critical role in supporting efficient proton pumping, by holding the heme groups in a proper environment.",
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N2 - The R481 residue in cytochrome c oxidase from Rhodobacter sphaeroides forms hydrogen bonds with the propionate groups of both heme a and heme a3. It has been postulated that R481 is the proton loading site in the proton exit pathway essential for proton translocation. A recent functional study showed that the mutations of R481 to His, Leu and Gln cause the reduction of the activity to ∼ 5-18% of the native level, and the absence of proton pumping in R481Q but retention of ∼ 40% efficiency in R481H and R481L (H.J. Lee, L. Öjemyr, A. Vakkasoglu, P. Brzezinski and R. B. Gennis, manuscript submitted). To decipher the molecular mechanism underlying the perturbed functionalities, we have used resonance Raman spectroscopy to examine the structural properties of the three mutants. The data show that the frequencies of the formyl C{double bond, short} O stretching modes of both the heme a and a3 in the mutants are characteristic of formyl groups exposed to an aqueous environment, indicating that the mutations disrupt the native H-bonding interaction between the formyl group of heme a and R52, as well as the hydrophobic environment surrounding the formyl group of heme a3. In addition to the change in the environments of heme a and a3, the Raman data show that the mutations induce a partial conversion of the heme a3 from a high-spin to a low-spin state, suggesting that the mutations are associated with the rearrangement of the CuB-heme a3 binuclear center. The Raman results reported here demonstrate that R481 plays a critical role in supporting efficient proton pumping, by holding the heme groups in a proper environment.

AB - The R481 residue in cytochrome c oxidase from Rhodobacter sphaeroides forms hydrogen bonds with the propionate groups of both heme a and heme a3. It has been postulated that R481 is the proton loading site in the proton exit pathway essential for proton translocation. A recent functional study showed that the mutations of R481 to His, Leu and Gln cause the reduction of the activity to ∼ 5-18% of the native level, and the absence of proton pumping in R481Q but retention of ∼ 40% efficiency in R481H and R481L (H.J. Lee, L. Öjemyr, A. Vakkasoglu, P. Brzezinski and R. B. Gennis, manuscript submitted). To decipher the molecular mechanism underlying the perturbed functionalities, we have used resonance Raman spectroscopy to examine the structural properties of the three mutants. The data show that the frequencies of the formyl C{double bond, short} O stretching modes of both the heme a and a3 in the mutants are characteristic of formyl groups exposed to an aqueous environment, indicating that the mutations disrupt the native H-bonding interaction between the formyl group of heme a and R52, as well as the hydrophobic environment surrounding the formyl group of heme a3. In addition to the change in the environments of heme a and a3, the Raman data show that the mutations induce a partial conversion of the heme a3 from a high-spin to a low-spin state, suggesting that the mutations are associated with the rearrangement of the CuB-heme a3 binuclear center. The Raman results reported here demonstrate that R481 plays a critical role in supporting efficient proton pumping, by holding the heme groups in a proper environment.

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