SPECIFICATION OF THE INHIBITORY-ACTION OF MIBG ON THE RESPIRATORY-CHAIN BY EPR SCANNING

In this paper we report EPR studies on the effects of meta-Iodobenzylg uanidine (MIBG), a structural analogue of norepinephrine capable of in hibiting complex I and III of the respiratory chain on the reduction s tate of the various complexes of the respiratory chain in beef heart s ubmitochondrial particles. The EPR spectrum of SMPs incubated with MIB G showed completely reduced prosthetic groups of complex I, but oxidis ed prosthetic groups of complex IV This indicates that complex I is in hibited by MIBG at the end of the complex (i.e. al the Q binding site) . Determination of the exact site of inhibition of MIBG on complex III yielded no conclusive results, but did confirm that complex III is in deed inhibited by MIBG.