Open AccessA cytochrome aa 3 ‐type quinol oxidase from Desulfurolobus ambivalens , the most acidophilic archaeon
Author(s) -
Anemüller S.,
Schmidt C.L.,
Pacheco I.,
Schäfer G.,
Teixeira M.
Publication year - 1994
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1994.tb06779.x
Subject(s) - heme a , heme , cytochrome , cytochrome c oxidase , redox titration , hemeprotein , chemistry , electron transport complex iv , redox , enzyme , biochemistry , oxidase test , stereochemistry , inorganic chemistry
Membranes of the extremely thermoacidophilic archaeon Desulfurolobus ambivalens grown under aerobic conditions contain a quinol oxidase of the cytochrome aa 3 ‐type as the most prominent hemoprotein. The partially purified enzyme consists of three polypeptide subunits with apparent molecular masses of 40, 27 and 20 kDa and contains two heme A molecules and one copper atom. CO difference spectra suggest one heme to be a heme a 3 ‐centre. The EPR spectra indicate the presence of a low‐spin and a high‐spin heme species. Redox titrations of the solubilized enzyme show the presence of two reduction processes, with apparent potentials of + 235 and + 330 mV. The enzyme cannot oxidize reduced cytochrome c , but rather serves as an oxidase of caldariella quinone. Due to their very simple composition, D . ambivalens cell appear as a promising candidate to study Structure‐function relationships of cytochrome aa 3 in the integral membrane state.