Mitochondrial nitric oxide production supported by reverse electron transfer

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

ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2016 vol. 607 p. 8 - 19

0003-9861

Heart phosphorylating electron transfer particles (ETPH) produced NO at 1.2 ± 0.1 nmol NO.min1 mg protein1 by the mtNOS catalyzed reaction. These particles showed a NADþ reductase activity of 64 ± 3 nmol min1 mg protein1 sustained by reverse electron transfer (RET) at expenses of ATP and succinate. The same particles, without NADPH and in conditions of RET produced 0.97 ± 0.07 nmol NO. min1 mg protein1. Rotenone inhibited NO production supported by RET measured in ETPH and in coupled mitochondria, but did not reduce the activity of recombinant nNOS, indicating that the inhibitory effect of rotenone on NO production is due to an electron flow inhibition and not to a direct action on mtNOS structure. NO production sustained by RET corresponds to 20% of the total amount of NO released from heart coupled mitochondria. A mitochondrial fraction enriched in complex I produced 1.7 ± 0.2 nmol NO. min1 mg protein1 and reacted with anti-75 kDa complex I subunit and anti-nNOS antibodies, suggesting that complex I and mtNOS are located contiguously. These data show that mitochondrial NO production can be supported by RET, and suggest that mtNOS is next to complex I,reaffirming the idea of a functional association between these proteins.