Premium
Characteristic differences in the mode of quinone reduction and stability between energy‐coupled and ‐uncoupled NADH‐quinone reductases from bacterial respiratory chain
Author(s) -
Unemoto Tsutomu,
Miyoshi Tohoru,
Hayashi Maki
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80835-5
Subject(s) - quinone , respiratory chain , chemistry , reduction (mathematics) , chain (unit) , photochemistry , biochemistry , physics , enzyme , mathematics , quantum mechanics , geometry
Bacterial respiratory chain has two types of NADH‐quinone reductase (NQR): one is energy‐coupled (type‐1) and the other has 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.