Isolation and characterization of a cDNA encoding the alpha' subunit of human cone cGMP-phosphodiesterase

A human cDNA (alpha-PDE) encoding the alpha' catalytic subunit of cone photoreceptor cGMP-phosphodiesterase has been isolated and characterized. The nucleotide sequence of 2980 bp contains an open reading frame encoding an 859-amino-acid (aa) protein with a calculated molecular mass of 99 kDa. Northern blot analysis of human retinal mRNA hybridized with the alpha'-PDE cDNA revealed a signal corresponding to a 3.2-kb transcript. Comparison of the deduced aa sequence of human cone alpha'-PDE with corresponding proteins isolated from bovine and chicken retinas shows 89 and 83% identity, respectively, and indicates that alpha'-PDE has been very well conserved in the evolutionary process. Human cone alpha'-PDE is highly homologous to rod alpha-PDE and beta-PDE, suggesting that these proteins may have a close phylogenetic relationship.