Figure 5.

Proposed mechanism for the interaction of NO with the catalytic intermediates of the mycobacterial bcc-aa₃ supercomplex under aerobic conditions. As shown for mtCcOX, by reacting with the intermediates O, P and F, NO is suggested to lead to formation of nitrite. However, at variance from the mammalian enzyme, in the case of the mycobacterial supercomplex, the observed NO/O₂ stoichiometry = 2.65 ± 0.19 suggests that nitrite does not bind with high affinity to oxidized haem a₃ and is rapidly ejected from the enzyme, without affecting its catalytic activity.