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.