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 the key enzymes of the visual phototransduction cascade in the vertebrate retina. The holoenzyme is a heterotetrameric complex, consisting of two large catalytic subunits, alpha (88 kDa) and beta (84 kDa), and two identical inhibitory subunits, gamma (11 kDa). Here we present the complete 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 acids and consists of four exons interrupted by three introns. The first intron is located in the 5'-untranslated region. The 5'-flanking region contains TATA-like and CAAT boxes which may serve as regulatory elements. The 5'-untranslated sequence (exon I) includes a potential SP1 transcription 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.