Functional interaction between complex I and mtNOS

VALDEZ LB; BOMBICINO SS; IGLESIAS DE; ZAOBORNYJ T; BOVERIS A

Buenos Aires

Congreso; VIII Meeting of the Society for Free Radical Biology and Medicine, South American Group; 2013

Society for Free Radical Biology and Medicine, South American Group

Not only complex IV (Persichini et al., 2006) but also complex I proteins (Franco et al., 2006) immunoprecipitate with mtNOS, suggesting physical interactions between mtNOS and complexes I and IV proteins. The aim of this work was to characterize the functional interaction between complex I and mtNOS using phosphorylating electron transfer particles (ETPH-Mg2+), that expose NADH dehydrogenase and mtNOS to the surrounding medium. NAD+ reductase activity (14.4±0.9 nmol/min.mg protein) sustained by reversed electron flow of the respiratory chain was inhibited by the addition of rotenone (88%), oligomycin (98%), antimycin (77%) and m-CCCP (93%). ETPH-Mg2+ produced NO at a rate of 0.62±0.03 nmol/min.mg protein; this production -supported by reversed flow- was still detectable (99%) in the absence of an exogenous electron donor (NADPH), suggesting that mtNOS activity could be sustained by electrons derived from the respiratory chain. Rotenone inhibited NO production (86%) supported by reversed electron flow, but it did not inhibit the activity of isolated nNOS, indicating that its inhibitory effect is due to an electron flow inhibition and not to a direct action on mtNOS structure. Preliminary results showed that isolated complex I from bovine heart mitochondria is recognized by anti nNOS-antibodies. To conclude, mtNOS could interact with complex I proteins using electrons derived from the respiratory chain for its enzymatic activity.