Structure of the <i>Euglena gracilis</i> chloroplast gene (<i>psbA</i>) coding for the 32-kDa protein of Photosystem II

An <i>Eco</i>RI fragment from <i>Euglena gracilis</i> chloroplast DNA, called Eco.I (4.9 kbp), contains the gene for the ‘32-kDa’ thylakoid membrane protein of Photosystem II (<i>psb</i> A gene), the tRNA₂</sup>Leu</sup> 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 <i>M</i>_r 38380 (345 amino acids). The <i>Euglena</i> protein is about 87% homologous with the higher plant counterparts but it contains 5 lysine residues.