Studies on the NADH-menaquinone oxidoreductase segment of the respiratory chain in Thermus thermophilus HB-8

• Published in: The Journal of biological chemistry Vol. 265; no. 3; pp. 1360 - 1368
• Main Authors: Meinhardt, S W, Wang, D C, Hon-nami, K, Yagi, T, Oshima, T, Ohnishi, T
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 25-01-1990
• Subjects: Cell Membrane - physiology; Cell Membrane - ultrastructure; Electron Spin Resonance Spectroscopy; Electron Transport; electron transport chain; Free Radicals; Iron-Sulfur Proteins - metabolism; Membrane Potentials; Metalloproteins - metabolism; NADH-menaquinone oxidoreductase; Oxidation-Reduction; Pyridines - pharmacology; Quinone Reductases - metabolism; Quinones; Thermus - enzymology; Thermus - ultrastructure
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)40022-7

Five distinct low potential iron-sulfur clusters have been identified potentiometrically in the membrane particles from Thermus
thermophilus HB-8. Three of these clusters (designated as [N-1H]T, [N-2H]T, and [N-3]T) exhibit the following midpoint redox
potentials and g values (Em8.0 = -274 mV, gx,y,z = 1.93, 1.94, 2.02), (Em8.0 = -304 mV, gx,y,z = 1.89, 1.95, 2.04), and (Em8.0
= -289 mV, gx,y,z = 1.80, 1.83, 2.06), respectively. These clusters, one binuclear and two tetranuclear, have been shown to
be components of the energy coupled NADH-menaquinone oxidoreductase complex (NADH dh I). They are reducible by NADH in the
piericidin A-inhibited aerobic membrane particles as well as in the purified NADH dh I complex. Two additional very low potential
iron-sulfur clusters (one binuclear, [N-1L]T, and one tetranuclear, [N-2L]T) were observed in membrane particles. These clusters
possess the following physiochemical properties (Em8.0 = -418 mV, gx,y,z = 1.93, 19.5, 2.02) and (Em8.0 = -437 mV, gx,y,z
= 1.89, 1.95, 2.04), respectively. No high potential tetranuclear cluster equivalent to the mitochondrial iron-sulfur cluster
[N-2]B was found in this bacterial system. In membrane particles isolated from T. thermophilus HB-8 cells, four different
semiquinone species have been identified based on their redox midpoint potentials [Em9(Q/QH2) = 40, -100, -160, -300 mV] and
sensitivity to the quinone analogue inhibitor, 2-heptyl-4-hydroxy quinoline-N-oxide. Of these semiquinone species the -100
mV component has been suggested to be part of the NADH dehydrogenase. Piericidin A sensitive delta psi formation has been
demonstrated to be coupled to the NADH-MQ1 oxidoreductase in membrane vesicles of T. thermophilus HB-8.