ISSN:
1573-6881
Keywords:
Terminal oxidase
;
cytochrome cbb 3
;
thermophile
;
Rhodothermus
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract Rhodothermus (R.) marinus, a thermohalophilic Gram-negative, and strict aerobic bacterium,has a rather distinct respiratory chain, containing a caa 3 terminal oxidase, a novel cytochromebc complex and a HiPIP, which is an electron carrier between this complex and a terminaloxidase (Pereira et al (1999a, c). To further elucidate this unusual respiratory system, itsmembrane-bound heme centers were characterized by visible and EPR spectroscopies as wellas by redox potentiometry. Rhodothermus marinus contains mostly B- and C-type hemes; asmall amount of A-type heme is also detected. The heme centers have relatively low reductionpotentials, ranging from ca. +250 to −60 mV, at pH 7. A Rieske-type center was not detected,suggesting the absence of a canonical complex III. The major terminal oxidase expressed byR. marinus is a cbb 3-type oxidase. Its presence is in agreement with molecular biology studies,which reveal the existence of a gene encoding for a FixN-type oxidase. The oxidase waspartially purified and appears to have five subunits, with apparent molecular masses of 64,57, 36, 26 (C-type heme subunit), and 13 kDa. It contains two low-spin heme C centers, onehigh-, and one low-spin heme B centers. A full description of the equilibrium redox behaviorof the heme centers was obtained for a cbb 3 oxidase for the first time. The optical spectrumfor each heme center and the corresponding reduction potentials were determined at pH 7:+ 195 (heme C), +120 (heme B), −50 (heme C), and −50 mV (heme B3).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1005555829301
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