The Euglena gracilis chloroplast ribulose-1,5-bisphosphate carboxylase gene. II. The spliced mRNA and its product.

The polypeptide product of the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase from Euglena gracilis based on the DNA sequence of the chloroplast-encoded gene is described. The large subunit polypeptide of 475 codons is co-linear with the homologous polypeptides from other chloroplasts and cyanobacteria. The amino acid sequence is 92% homologous to that of Chlamydomonas, 84% homologous to spinach, 82% homologous to maize, and 80% homologous to that of the cyanobacterium Anabaena variabilis. Known functional domains of the protein are coded by the larger exons of the gene. Introns in the gene generally occur at coding sequences specifying hydrophilic, presumably surface exposed, regions of the polypeptide. The location of some of the introns may reflect a separation of functional domains. The 5'- and 3'-ends of the rbcL transcript were determined by primer extension sequencing using reverse transcriptase and S1 nuclease protection, respectively. The transcribed but untranslated sequences are quite distinct from those from other rbcL loci.