Exploring the proton pump and exit pathway for pumped protons in cytochrome ba 3 from Thermus thermophilus

Hsin Yang Chang, Sylvia K. Choi, Ahmet Selim Vakkasoglu, Ying Chen, James Hemp, James A. Fee, Robert B. Gennis

Research output: Contribution to journalArticle

Abstract

The heme-copper oxygen reductases are redox-driven proton pumps. In the current work, the effects of mutations in a proposed exit pathway for pumped protons are examined in the ba 3-type oxygen reductase from Thermus thermophilus, leading from the propionates of heme a 3 to the interface between subunits I and II. Recent studies have proposed important roles for His376 and Asp372, both of which are hydrogen-bonded to propionate-A of heme a 3, and for Glu126 II (subunit II), which is hydrogen-bonded to His376. Based on the current results, His376, Glu126 II, and Asp372 are not essential for either oxidase activity or proton pumping. In addition, Tyr133, which is hydrogen-bonded to propionate-D of heme a 3, was also shown not to be essential for function. However, two mutations of the residues hydrogen-bonded to propionate-A, Asp372Ile and His376Asn, retain high electron transfer activity and normal spectral features but, in different preparations, either do not pump protons or exhibit substantially diminished proton pumping. It is concluded that either propionate-A of heme a 3 or possibly the cluster of groups centered about the conserved water molecule that hydrogen-bonds to both propionates-A and -D of heme a 3 is a good candidate to be the proton loading site.

Original languageEnglish (US)
Pages (from-to)5259-5264
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number14
DOIs
StatePublished - Apr 3 2012

Keywords

  • Bioenergetics
  • Cytochrome c oxidase
  • Exit channel
  • Respiratory chain

ASJC Scopus subject areas

  • General

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