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. 1977 Aug 1;165(2):295–301. doi: 10.1042/bj1650295

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 1, C Ian Ragan 1,*
PMCID: PMC1164901  PMID: 411483

Abstract

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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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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