CLONING AND CHARACTERIZATION OF THE GENE ENCODING THE CGMP-PHOSPHODIESTERASE GAMMA-SUBUNIT OF HUMAN ROD PHOTORECEPTOR CELLS

Rod photoreceptor cyclic GMP-phosphodiesterase (cGMP-PDE) is one of th e key enzymes of the visual phototransduction cascade in the vertebrat e retina. The holoenzyme is a heterotetrameric complex, consisting of two large catalytic subunits, alpha (88 kDa) and beta (84 kDa), and tw o identical inhibitory subunits, gamma (11 kDa). Here we present the c omplete nucleotide sequence of the gene (cGMP-PDE gamma) encoding the cGMP-PDE gamma-subunit from human rod photoreceptors. The transcribed region of the human cGMP-PDE gamma codes for a protein of 87 amino aci ds and consists of four exons interrupted by three introns. The first intron is located in the 5'-untranslated region. The 5'-flanking regio n contains TATA-like and CAAT boxes which may serve as regulatory elem ents. The 5'-untranslated sequence (exon I) includes a potential SP1 t ranscription factor-binding site (GC core hexanucleotide). In addition , there were five AluI repetitive elements found in the cGhM-PDE gamma , three in the first intron and two in the second intron.