Taxonomic distribution of proteins containing Haem_bd domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing Haem_bd domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Molecular characterization of the membrane-bound quinol peroxidase functionallyconnected to the respiratory chain.

Yamada H, Takashima E, Konishi K
FEBS J. 2007; 274: 853-66

Here, we report for the first time quinol peroxidase (QPO), an enzyme that usesubiquinol-1 as an electron donor for the reduction of H(2)O(2) to water. Wepurified QPO to > 90% purity from the membrane fraction of Actinobacillusactinomycetemcomitans. QPO is a 53.6-kDa protein that contains three heme cmolecules. The qpo gene was predicted to encode a putative bacterial cytochrome cperoxidase with N-terminal extensions containing an additional potential hemec-binding motif. Although qpo has high sequence homology to bacterial cytochrome c peroxidases, QPO did not catalyze peroxidation in the presence of horse heartcytochrome c. In addition, the cytoplasmic membrane of A. actinomycetemcomitanshad apparent QPO-dependent peroxidase activity in the presence of NADH orsuccinate, which are substrates for the respiratory chain. Based on thesefindings, we present a new mechanism for the scavenging of reactive oxygenspecies in which quinol in the respiratory chain is consumed.