Four different b-type cytochromes in the halophilic archaebacterium, Halobacterium halobium

• Published in: Archives of biochemistry and biophysics Vol. 272; no. 1; pp. 130 - 136
• Main Authors: Hallberg Gradin, Christina, Colmsjö, Anders
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.07.1989; Elsevier
• Subjects: Analytical, structural and metabolic biochemistry; Antimycin A - analogs & derivatives; Antimycin A - pharmacology; Biological and medical sciences; Carbon Monoxide; Cell Membrane - analysis; cytochrome b; Cytochrome b Group - analysis; Cytochrome b Group - metabolism; Electron Transport; Fundamental and applied biological sciences. Psychology; Halobacterium - analysis; Hemoproteins; Metalloproteins; NAD - metabolism; Oxidation-Reduction; Oxygen - metabolism; Potentiometry; Proteins; Spectrophotometry; Succinates - metabolism; Succinic Acid; Hemoprotein; Oxidation reduction; Archaeobacteria; In situ; Electron transfer; Halobacterium halobium; Characterization; Cytochrome b; Plasma membrane; Potentiometric method; Microorganism culture; Bacteria; Isoform; Halobacteriaceae
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/0003-9861(89)90203-8

The halophilic archaebacterium, Halobacterium halobium has been found to contain four different b-type cytochromes. The four components were recognized by their potentiometric characteristics in situ in their functional environment in the membrane of H. halobium. Oxidation-reduction midpoint potentials of these four b-type cytochromes were determined to be +261, +160, +30, and −153 mV, respectively. We also demonstrate that the pathway involved in the transport of reducing equivalents from succinate to oxygen proceeds through the b-type cytochromes with oxidation-reduction midpoint potentials of +261 and +161 mV. The cytochrome with oxidation-reduction midpoint potential of −153 mV was not substrate reducible by NADH but was chemically reducible by dithionite. Antimycin inhibits reduction of b-type cytochrome in the succinate pathway, but has no effect on b-type cytochrome reduction when reducing equivalents are provided by NADH. The carbon monoxide difference spectrum of H. halobium membranes shows at least one carbon monoxide-binding b-type cytochrome, indicating a terminal oxidase. A scheme for electron transport in H. halobium involving the b-type cytochromes and terminal oxidases is suggested.