Unexpected stimulation of mitochondrial ADP‐ribosylation by cyanide

Publisher Website
Google Scholar
Abstract
Cyanide, the classical inhibitor of the mitochondrial respiratory chain at site III, stimulates ADP‐ribosylation of a number of mitochondrial proteins, the major protein being the 50–55 kDa band. Sodium azide, sharing the same inhibitory site, does not have the same effect. Rotenone or antimycin A have no influence on mitochondrial ADP‐ribosylation. Data suggest that no apparent correlation exists between oxidoreductase function and protein ADP‐ribosylation. Purified nuclear poly(ADP‐ribose) polymerase activity was not affected by cyanide. The cyanide effect on mitochondrial ADP‐ribosylation seems intriguing and may be attributed to NAD+ ‐CN complex formation, since NAD reacts with cyanide at pH > 8 with N‐substituted nicotinamide which may prevent inhibition of ADP‐ribosylation.