Phycocyanin alpha-subunit gene of Anacystis nidulans R2: cloning, nucleotide sequencing and expression in Escherichia coli.

The cloning and nucleotide sequence determination of the Anacystis nidulans R2 phycocyanin (PC) alpha-subunit gene are described. A 3.0-kb PstI fragment of Anacystis nidulans R2 genomic DNA cloned in plasmid pUC8 was found to hybridize with a heptadecameric oligodeoxynucleotide probe. Sequencing using synthetic primers revealed the presence of the PC alpha-subunit gene and the 3' proximal end of the beta-subunit gene. The alpha-gene is separated from the upstream beta-gene by a spacer length of 51 bp. The deduced amino acid (aa) sequence of the alpha-subunit protein is identical, except for 5 aa, to that of A. nidulans 6301 and is highly homologous (77%) to that reported for Agmenellum quadruplicatum PR6. The 16-kDa alpha-subunit protein, detected by immunoadsorption, was fortuitously expressed in Escherichia coli from the lacZ promoter of the cloning vehicle pUC8.