期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
卷 1817, 期 4, 页码 638-649出版社
ELSEVIER
DOI: 10.1016/j.bbabio.2011.08.004
关键词
ba(3)-oxidase; caa(3)-oxidase; Respiratory complex; Thermus thermophilus
资金
- Government of Ireland through the Science Foundation Ireland [BICF685]
- Irish Research Council for Science, Engineering and Technology (EMBARK Initiative)
Seven years into the completion of the genome sequencing projects of the thermophilic bacterium Thermus thermophilus strains HB8 and HB27, many questions remain on its bioenergetic mechanisms. A key fact that is occasionally overlooked is that oxygen has a very limited solubility in water at high temperatures. The HB8 strain is a facultative anaerobe whereas its relative HB27 is strictly aerobic. This has been attributed to the absence of nitrate respiration genes from the HB27 genome that are carried on a mobilizable but highly-unstable plasmid. In T. thermophilus, the nitrate respiration complements the primary aerobic respiration. It is widely known that many organisms encode multiple biochemically-redundant components of the respiratory complexes. In this minireview, the presence of the two cytochrome c oxidases (CcO) in T. thermophilus, the ba(3)- and caa(3)-types, is outlined along with functional considerations. We argue for the distinct evolutionary histories of these two CcO including their respective genetic and molecular organizations, with the caa(3)-oxidase subunits having been initially 'fused'. Coupled with sequence analysis, the ba(3)-oxidase crystal structure has provided evolutionary and functional information: for example, its subunit I is more closely related to archaeal sequences than bacterial and the substrate-enzyme interaction is hydrophobic as the elevated growth temperature weakens the electrostatic interactions common in mesophiles. Discussion on the role of cofactors in intra- and intermolecular electron transfer and proton pumping mechanism is also included. This article is part of a Special Issue entitled: Respiratory Oxidases. (C) 2011 Elsevier B.V. All rights reserved.
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