Blocking the K-pathway still allows rapid one-electron reduction of the binuclear center during the anaerobic reduction of the aa 3 -type cytochrome c oxidase from Rhodobacter sphaeroides

Krithika Ganesan, Robert B Gennis

Research output: Contribution to journalArticle

Abstract

The K-pathway is one of the two proton-input channels required for function of cytochrome c oxidase. In the Rhodobacter sphaeroides cytochrome c oxidase, the K-channel starts at Glu101 in subunit II, which is at the surface of the protein exposed to the cytoplasm, and runs to Tyr288 at the heme a 3 /Cu B active site. Mutations of conserved, polar residues within the K-channel block or inhibit steady state oxidase activity. A large body of research has demonstrated that the K-channel is required to fully reduce the heme/Cu binuclear center, prior to the reaction with O 2 , presumably by providing protons to stabilize the reduced metals (ferrous heme a 3 and cuprous Cu B ). However, there are conflicting reports which raise questions about whether blocking the K-channel blocks both electrons or only one electron from reaching the heme/Cu center. In the current work, the rate and extent of the anaerobic reduction of the heme/Cu center were monitored by optical and EPR spectroscopies, comparing the wild type and mutants that block the K-channel. The new data show that when the K-channel is blocked, one electron will still readily enter the binuclear center. The one-electron reduction of the resting oxidized ("O") heme/Cu center of the K362M mutant, results in a partially reduced binuclear center in which the electron is distributed about evenly between heme a 3 and Cu B in the R. sphaeroides oxidase. Complete reduction of the heme/Cu center requires the uptake of two protons which must be delivered through the K-channel.

Original languageEnglish (US)
Pages (from-to)619-624
Number of pages6
JournalBiochimica et Biophysica Acta - Bioenergetics
Volume1797
Issue number6-7
DOIs
StatePublished - Jun 1 2010

Fingerprint

Rhodobacter sphaeroides
Electron Transport Complex IV
Heme
Electrons
Protons
Oxidoreductases
Paramagnetic resonance
Catalytic Domain
Spectrum Analysis
Membrane Proteins
Cytoplasm
Metals
Spectroscopy
Mutation
Research
heme a

Keywords

  • Cytochrome oxidase
  • K-pathway
  • Protons
  • R. sphaeroides
  • Respiration

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

Cite this

@article{637d3a1bfdbf4b7fbf168311cb121300,
title = "Blocking the K-pathway still allows rapid one-electron reduction of the binuclear center during the anaerobic reduction of the aa 3 -type cytochrome c oxidase from Rhodobacter sphaeroides",
abstract = "The K-pathway is one of the two proton-input channels required for function of cytochrome c oxidase. In the Rhodobacter sphaeroides cytochrome c oxidase, the K-channel starts at Glu101 in subunit II, which is at the surface of the protein exposed to the cytoplasm, and runs to Tyr288 at the heme a 3 /Cu B active site. Mutations of conserved, polar residues within the K-channel block or inhibit steady state oxidase activity. A large body of research has demonstrated that the K-channel is required to fully reduce the heme/Cu binuclear center, prior to the reaction with O 2 , presumably by providing protons to stabilize the reduced metals (ferrous heme a 3 and cuprous Cu B ). However, there are conflicting reports which raise questions about whether blocking the K-channel blocks both electrons or only one electron from reaching the heme/Cu center. In the current work, the rate and extent of the anaerobic reduction of the heme/Cu center were monitored by optical and EPR spectroscopies, comparing the wild type and mutants that block the K-channel. The new data show that when the K-channel is blocked, one electron will still readily enter the binuclear center. The one-electron reduction of the resting oxidized ({"}O{"}) heme/Cu center of the K362M mutant, results in a partially reduced binuclear center in which the electron is distributed about evenly between heme a 3 and Cu B in the R. sphaeroides oxidase. Complete reduction of the heme/Cu center requires the uptake of two protons which must be delivered through the K-channel.",
keywords = "Cytochrome oxidase, K-pathway, Protons, R. sphaeroides, Respiration",
author = "Krithika Ganesan and Gennis, {Robert B}",
year = "2010",
month = "6",
day = "1",
doi = "10.1016/j.bbabio.2010.03.012",
language = "English (US)",
volume = "1797",
pages = "619--624",
journal = "Biochimica et Biophysica Acta - Bioenergetics",
issn = "0005-2728",
publisher = "Elsevier",
number = "6-7",

}

TY - JOUR

T1 - Blocking the K-pathway still allows rapid one-electron reduction of the binuclear center during the anaerobic reduction of the aa 3 -type cytochrome c oxidase from Rhodobacter sphaeroides

AU - Ganesan, Krithika

AU - Gennis, Robert B

PY - 2010/6/1

Y1 - 2010/6/1

N2 - The K-pathway is one of the two proton-input channels required for function of cytochrome c oxidase. In the Rhodobacter sphaeroides cytochrome c oxidase, the K-channel starts at Glu101 in subunit II, which is at the surface of the protein exposed to the cytoplasm, and runs to Tyr288 at the heme a 3 /Cu B active site. Mutations of conserved, polar residues within the K-channel block or inhibit steady state oxidase activity. A large body of research has demonstrated that the K-channel is required to fully reduce the heme/Cu binuclear center, prior to the reaction with O 2 , presumably by providing protons to stabilize the reduced metals (ferrous heme a 3 and cuprous Cu B ). However, there are conflicting reports which raise questions about whether blocking the K-channel blocks both electrons or only one electron from reaching the heme/Cu center. In the current work, the rate and extent of the anaerobic reduction of the heme/Cu center were monitored by optical and EPR spectroscopies, comparing the wild type and mutants that block the K-channel. The new data show that when the K-channel is blocked, one electron will still readily enter the binuclear center. The one-electron reduction of the resting oxidized ("O") heme/Cu center of the K362M mutant, results in a partially reduced binuclear center in which the electron is distributed about evenly between heme a 3 and Cu B in the R. sphaeroides oxidase. Complete reduction of the heme/Cu center requires the uptake of two protons which must be delivered through the K-channel.

AB - The K-pathway is one of the two proton-input channels required for function of cytochrome c oxidase. In the Rhodobacter sphaeroides cytochrome c oxidase, the K-channel starts at Glu101 in subunit II, which is at the surface of the protein exposed to the cytoplasm, and runs to Tyr288 at the heme a 3 /Cu B active site. Mutations of conserved, polar residues within the K-channel block or inhibit steady state oxidase activity. A large body of research has demonstrated that the K-channel is required to fully reduce the heme/Cu binuclear center, prior to the reaction with O 2 , presumably by providing protons to stabilize the reduced metals (ferrous heme a 3 and cuprous Cu B ). However, there are conflicting reports which raise questions about whether blocking the K-channel blocks both electrons or only one electron from reaching the heme/Cu center. In the current work, the rate and extent of the anaerobic reduction of the heme/Cu center were monitored by optical and EPR spectroscopies, comparing the wild type and mutants that block the K-channel. The new data show that when the K-channel is blocked, one electron will still readily enter the binuclear center. The one-electron reduction of the resting oxidized ("O") heme/Cu center of the K362M mutant, results in a partially reduced binuclear center in which the electron is distributed about evenly between heme a 3 and Cu B in the R. sphaeroides oxidase. Complete reduction of the heme/Cu center requires the uptake of two protons which must be delivered through the K-channel.

KW - Cytochrome oxidase

KW - K-pathway

KW - Protons

KW - R. sphaeroides

KW - Respiration

UR - http://www.scopus.com/inward/record.url?scp=77953812499&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77953812499&partnerID=8YFLogxK

U2 - 10.1016/j.bbabio.2010.03.012

DO - 10.1016/j.bbabio.2010.03.012

M3 - Article

C2 - 20307488

AN - SCOPUS:77953812499

VL - 1797

SP - 619

EP - 624

JO - Biochimica et Biophysica Acta - Bioenergetics

JF - Biochimica et Biophysica Acta - Bioenergetics

SN - 0005-2728

IS - 6-7

ER -