A synthetic COOH-terminal oligopeptide of D1 protein deduced from the spinach psbA gene (Asn-325-Gly-353) was subjected to proteolytic digestion by purified processing enzyme of D1 protein [(1989) FEBS Lett. 246, 218–222] and the following two fragments were obtained as cleavage products: a COOH-terminal 9-amino-acid fragment (Ala-345-Gly-353) and an NH2-terminal 10-amino-acid fragment (Asn-325-Arg-334). It was concluded that: (i) the oligopeptide consisting of the COOH-terminal 29-amino-acid sequence deduced from the spinach psbA gene provides the recognition domain for the processing enzyme; (ii) the cleavage takes place at the predicted processing site of native DI precursor protein (COOH side of Ala-344); and (iii) another cleavage takes place at an additional site (COOH side of Arg-334) for the synthetic substrate, but not for the native D1 precursor protein.
