Nucleotide sequence and phylogenetic implication of the ATPase subunits beta and epsilon encoded in the chloroplast genome of the brown alga Dictyota dichotoma.

We have cloned and sequenced the genes atpB and atpE, coding for CF1 subunits beta and epsilon, respectively, of the chloroplast genome of the brown alga Dictyota dichotoma. Although the coding site of atpE cannot be demonstrated by heterologous Southern hybridizations, a 417 bp reading frame 3' to atpB was identified as the gene atpE by sequence similarities with atpE genes from other sources. A maximum sequence identity of 30% is found between the predicted amino acid sequence of the Dictyota subunit epsilon and the corresponding cyanobacterial subunits. Including conserved amino acid replacements, the Dictyota epsilon subunit exhibits about 70% sequence similarity with the cyanobacterial and land plant subunits. As in cyanobacteria, the atpE gene does not overlap the preceding gene atpB. The deduced amino acid sequence of atpB is 74-79% identical to the corresponding cyanobacterial and chloroplast subunits. Entirely conserved are regions referred to as the catalytic and/or regulatory sites of ATP formation, including interacting regions between subunits alpha and beta. A phylogram predicted from F1/CF1-beta subunits of eleven different organisms suggests a common evolutionary origin of plastids from chlorophytes and brown algae.