1. Incubation of NADH–ubiquinone oxidoreductase (Complex I) with chymotrypsin caused loss of rotenone-sensitive ubiquinone-1 reduction and an increase in rotenone-insensitive ubiquinone reduction. 2. Within the same time-course, NADH–K3Fe(CN)6 oxidoreductase activity was unaffected. 3. Mixing of chymotrypsin-treated Complex I with Complex III did not give rise to NADH–cytochrome c oxidoreductase activity. 4. Gel electrophoresis in the presence of sodium dodecyl sulphate revealed selective degradation of several constituent polypeptides by chymotrypsin. 5. With higher chymotrypsin concentrations and longer incubation times, a decrease in NADH–K3Fe(CN)6 oxidoreductase was observed. The kinetics of this decrease correlated with solubilization of the low-molecular-weight type-II NADH dehydrogenase (subunit mol.wts. 53000 and 27000) and with degradation of a polypeptide of mol.wt. 30000. 6. Phospholipid-depleted Complex I was more rapidly degraded by chymotrypsin. Specifically, a subunit of mol.wt. 75000, resistant to chymotrypsin in untreated Complex I, was degraded in phospholipid-depleted Complex I. In addition, the 30000-mol.wt. polypeptide was also more rapidly digested, correlating with an increased rate of transformation to type II NADH dehydrogenase.
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August 1977
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Research Article|
August 01 1977
Effects of proteolytic digestion by chymotrypsin on the structure and catalytic properties of reduced nicotinamide–adenine dinucleotide–ubiquinone oxidoreductase from bovine heart mitochondria
Susan E. Crowder;
Susan E. Crowder
1Department of Physiology and Biochemistry, University of Southampton, Southampton SO9 3TU, U.K.
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C. Ian Ragan
C. Ian Ragan
1Department of Physiology and Biochemistry, University of Southampton, Southampton SO9 3TU, U.K.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1977 London: The Biochemical Society
1977
Biochem J (1977) 165 (2): 295–301.
Citation
Susan E. Crowder, C. Ian Ragan; Effects of proteolytic digestion by chymotrypsin on the structure and catalytic properties of reduced nicotinamide–adenine dinucleotide–ubiquinone oxidoreductase from bovine heart mitochondria. Biochem J 1 August 1977; 165 (2): 295–301. doi: https://doi.org/10.1042/bj1650295
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