[Dicyclohexylcarbodiimide as an inhibitor of light- and pyrophosphate-induced formation of membrane potential in chromatophores of purple bacteria].

N,N'-Dicyclohexylcarbodiimide (DCCD) suppresses the uptake of penetrating tetraphenylborate anions by Rhodospirillum rubrum chromatophores during cyclic and non-cyclic electron transfer and ATP and PP i hydrolyses. The photochemical activity of the bacteriochlorophyll reaction centers of the chromatophores in insensitive to DCCD. This supports the view that DCCD inhibits the electron transfer between the primary and secondary quinones of the photosynthetic chain. Incorporation of the chromatophores into a planar phospholipid-decane membrane abolishes or considerably reduces the inhibiting effect of DCCD on the membrane potential generation during the light-induced electron transfer and PP i (but not ATP) hydrolysis. The inhibition of the photosynthetic electron transfer is proposed to be due to the effect of DCCD as a quinone antagonist which competes with the secondary quinone for the binding at the active site. By expelling quinones DCCD seems to destroy the specific microenvironment of PPiase in the membrane and to inhibit its catalytic activity. In the system with the planar membrane decane and/or phospholipids remove the effect of DCCD as a quinone antagonist.