A cytochrome aa3-type quinol oxidase from Desulfurolobus ambivalens, the most acidophilic archaeon |
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| Authors: | S Anemüller CL Schmidt I Pacheco G Schäfer M Teixeira |
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| Institution: | Institut für Biochemie, Medizinische Universität zu Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, FRG; Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Apt. 127, Rua da Quinta Grande 6, P-2780 Oeiras, Portugal |
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| Abstract: | Abstract 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. |
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| Keywords: | Desulfurolobus ambivalens Archaea Quinol oxidase Cytochrome aa3 Cooper Reduction potential EPR |
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