Characteristic differences in the mode of quinone reduction and stability between energy-coupled and -uncoupled NADH-quinone reductases from bacterial respiratory chain.
Bacterial respiratory chain has two types of NADH-quinone reductase (NQR): one is energy-coupled (type-1) and the other had no energy-transducing capacity, that is, energy-uncoupled (type-2). Each of the NADH-reacting flavoprotein subunits of NQR-1 from Escherichia coli and the marine Vibrio alginolyticus reduced quinone to semiquinone radicals by the one-electron transfer pathway and was very sensitive to preincubation with NADH. On the other hand, the NQR-2 from these bacteria reduced quinone to quinol by the two-electron transfer pathway and was insensitive to preincubation with NADH. Since the NQR-1 from E. coli functions as a proton pump, whereas that from the marine V. alginolyticus functions as a sodium pump, the formation of semiquinone radicals as an intermediate is likely to be a common mechanism to functioning as either proton or sodium pump.
Unemoto
T
T
Laboratory of Membrane Biochemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Miyoshi
T
T
Hayashi
M
M
D004926:Escherichia coli / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D011808:Quinone Reductases / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism*; D014733:Vibrio / Q000201:enzymology*
D011809:Quinones; D009243:NAD; D011808:Quinone Reductases