An EcoRI fragment from Euglena gracilis chloroplast DNA, called Eco.I (4.9 kbp), contains the gene for the ‘32-kDa’ thylakoid membrane protein of Photosystem II ( psb A gene), the tRNA 2 Leu gene and additional sequences which possibly code for two proteins of unknown function. The transcription polarity is the same for all these coding sequences. The psb A gene is split: 4 introns (size range, 433–616 bp) separate 5 exons (size range, 39–579 bp) which code for a protein of M r 38380 (345 amino acids). The Euglena protein is about 87% homologous with the higher plant counterparts but it contains 5 lysine residues. Euglena gracilis Chloroplast genome psbA trnL