The 15-kDa forms of the apo-peridinin-chlorophyll a protein (PCP) in dinoflagellates show high identity with the apo-32 kDa PCP forms, and have similar N-terminal leaders and gene arrangements

Full-length genomic sequences encoding apo peridinin-chlorophyll et protein s (PCPs) from Heterocapsa pygmaea have been obtained by PCR. Two of the der ived mature proteins of 150 residues have molecular masses of 15,795 and 15 ,780, respectively. Contrary to an earlier report, these show a high degree of identity (similar to 70%) over the whole of both domains to the mature 32-kDa PCP forms. The two genes lack introns, are arranged in tandem and se parated by 526 bp. A putative N-terminal extension with three domains chara cteristic of a signal sequence, a chloroplast-targeting sequence and a thyl akoid lumen-directing sequence, is present. Modelling of the Heterocapsa PC P amino acid sequence on to the high-resolution structure available for Amp hidinium PCP shows that the main differences between two forms are in trime r contact regions.