THE HUMAN ROD PHOTORECEPTOR CGMP PHOSPHODIESTERASE BETA-SUBUNIT STRUCTURAL STUDIES OF ITS CDNA AND GENE

cDNA clones encoding the beta-subunit of the photoreceptor cGMP phosph odiesterase (PDE) were isolated from a human retina library and their sequence was determined. The encoded polypeptide consists of 854 amino acid residues with a calculated molecular mass of 98,416 Da. Alignmen t of the deduced amino acid sequence with the earlier analysed alpha-, beta- and alpha'-subunits of bovine and mouse PDEs demonstrates a hig h homology. Two overlapping recombinant lambda phage clones containing 26 kb of the human PDE beta-subunit gene were isolated from the genom ic library. A total nucleotide sequence of exons 4-22 of the PDE beta- subunit gene was established which completely corresponded to the cDNA structure. According to sequence analysis no potential possibility fo r alternative splicing of the beta-subunit gene was observed between e xons 20 and 21 which led to the formation of the beta'-subunit as desc ribed for mouse PDE. Polymerase chain reaction (PCR) experiments also confirm the absence of the PDE beta'-subunit in human retina.