COOH-terminal residues of D1 and the 44 kDa CPa-2 at spinach photosystem II core complex

The COOH-termini of the 32 kDa D1 and 44 kDa CPa-2 were determined by protein sequencing of peptides from trypsinized photosystem II core complexes. COOH-terminal fragments were isolated by affinity chromatography using anhydrotrypsin-agarose. One peptide had a sequence corresponding to the segment from Asn at position 335 to Ala at position 344 of the sequence deduced from the psbA gene coding for D1. Nine amino acids may be cleaved from the COOH-terminus of pre-D1 during maturation. In contrast, CPa-2 was not modified at its COOH-terminus.