The Chloroplast ATP Synthase in Chlamydomonas reinhardtii

Claire Lemaire (1) , Francis-André Wollman (1)

1 I2BC - Institut de Biologie Intégrative de la Cellule

We have characterized the subunit composition of the chloroplast ATP synthase from $Chlamydomonas\ reinhardtii$ by means of a comparison of the polypeptide deficiencies in a mutant defective in photophosphorylation, with the polypeptide content in purified coupling factor (CF)$_1$ and CF$_1$-CF$_O$ complexes. We could distinguish nine subunits in the enzyme, four of which were CF, subunits. Further characterization of these subunits was undertaken by immunoblotting experiments , [$^{14}$C]dicyclohexylcarbodiimide binding and analysis of their site of translation. In particular, we were able to show the presence of an as yet unidentified $\delta$ subunit in CF$_1$ from $C.\ reinhardtii$. We have identified a 70-kDa peripheral membrane protein in the thylakoid membranes of $C.\ reinhardtii$, which is immunologically related to the $\beta$l subunit of CF$_1$. We discuss its conceivable ATPase function with respect to the Ca$^{2+}$ -dependent ATPase activity previously reported in the thylakoid membranes from $C.\ reinhardtii$ (Piccioni, R. G., Bennoun, P., and Chua, N. H. (1981) Eur. J. Biochem. 117,93-102).

Domaines: Sciences du Vivant [q-bio]

Claire Lemaire, Francis-André Wollman. The Chloroplast ATP Synthase in Chlamydomonas reinhardtii: I. Characterization of its nine constitutive subunits. Journal of Biological Chemistry, 1989, 264 (17), pp.10228-10234. ⟨cea-02474816⟩