Alkylation of cysteine 89 of the gamma subunit of chloroplast coupling factor 1 with N-ethylmaleimide alters nucleotide interactions.

Alkylation of Cys-89 of the y subunit of the coupling factor portion (CF,) of the chloroplast ATP synthase by N-ethylmaleimide was previously shown to inhibit ATP synthesis and hydrolysis. The y subunit interacts with the inhibitory Q subunit. Alkylation of y Cys-89 could cause changes that result in the strengthening of the interactions between the two subunits which would be inhibitory, We show that the inhibition of the ATPase activity of CF, in solution persists after removal of the a subunit. Additionally, a rebinds to control and alkylated CF, at very similar CF, to a concentration ratios.