Oct 7, 2009

The cytochrome ba3 oxygen reductase from Thermus thermophilus uses a single input channel for proton delivery to the active site and for proton pumping

Proceedings of the National Academy of Sciences of the United States of America
Hsin-Yang ChangRobert B Gennis


The heme-copper oxygen reductases are redox-driven proton pumps that generate a proton motive force in both prokaryotes and mitochondria. These enzymes have been divided into 3 evolutionarily related groups: the A-, B- and C-families. Most experimental work on proton-pumping mechanisms has been performed with members of the A-family. These enzymes require 2 proton input pathways (D- and K-channels) to transfer protons used for oxygen reduction chemistry and for proton pumping, with the D-channel transporting all pumped protons. In this work we use site-directed mutagenesis to demonstrate that the ba(3) oxygen reductase from Thermus thermophilus, a representative of the B-family, does not contain a D-channel. Rather, it utilizes only 1 proton input channel, analogous to that of the A-family K-channel, and it delivers protons to the active site for both O2 chemistry and proton pumping. Comparison of available subunit I sequences reveals that the only structural elements conserved within the oxygen reductase families that could perform these functions are active-site components, namely the covalently linked histidine-tyrosine, the Cu(B) and its ligands, and the active-site heme and its ligands. Therefore, our data suggest that all...Continue Reading

  • References42
  • Citations52


Mentioned in this Paper

Biochemical Pathway
Cytochrome c Oxidase Subunit VIa
Bacterial Proteins
Enzymes, antithrombotic
Cytochrome Reductases
Mutagenesis, Site-Directed
Tertiary Protein Structure
Thermus thermophilus extract

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