Phycocyanin (PC) is a light-harvesting protein common to blue-green and red algae. We have isolated the genes for the two apoprotein subunits, α and β, of PC from the blue-green alga Agmenellum quadruplicatum PR-6. We synthesized eight sense-strand tetradecameric oligonucleotide probes that could encode a particular pentapeptide in PCα from A. quadruplicatum. Only one probe hybridized with total RNA from this organism. This oligonucleotide showed homology to a unique restriction fragment when used to probe Southern blots of A. quadruplicatum DNA. The probe-homologous 3.1-kilobase pair HindIII fragment was cloned. The nucleotide sequence of a 1.7-kilobase pair segment of this clone was determined. Two open reading frames are contained in this region, which correspond in deduced amino acid sequence to PCα and PCβ subunits. Both coding sequences are in the same orientation, separated by 105 base pairs, with the PCβ gene 5' to the PCα gene. Each gene has a Shine-Dalgarno-type sequence near the initiation codon. Codon frequencies in the two genes may be correlated with the abundance of their products. The deduced amino acid sequences of the gene products show considerable homology with the α and β PC subunits from other species.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Issue number||24 I|
|State||Published - 1984|
All Science Journal Classification (ASJC) codes