Rod structure of a phycoerythrin II-containing phycobilisome. I. Organization and sequence of the gene cluster encoding the major phycobiliprotein rod components in the genome of marine Synechococcus sp. WH8020.

Phycobilisomes of the unicellular marine cyanobacteria are unique in having rod substructures with two distinct phycoerythrins, PE I and PE II, with five and six bilins, respectively (Ong, L. J., and Glazer, A. N. (1991) J. Biol. Chem. 266, 9515-9527). The genes for the alpha and beta subunits of PE I, PE II, and phycocyanin, and that for the PE II-associated linker polypeptide, are clustered on a single 15-kilobase region of the genome of Synechococcus sp. WH8020. Complete sequencing of this region allowed definitive assignment of the positions of all bilin attachment sites in these phycobiliproteins. Twelve other open reading frames are closely associated with the structural genes specified above. Six are homologous to open reading frames adjacent to phycobiliprotein genes in other cyanobacteria and inferred to be involved in bilin addition. This is the largest number of open reading frames of this class known in any cyanobacterium. Another of the open reading frames has a short region of striking similarity to the active site sequence of a bovine protein-phosphotyrosine phosphatase.