Molecular Analysis of the Human GAR1 Gene
A bovine glutamic acid rich protein (garp) was first reported as a soluble protein of unknown function which copurified with cGMP phosphodiesterase from rod outer segments (1). Characterization of bovine retina cDNA clones encoding garp identified a 65 kD protein with a high overall glutamate composition (24%), including one 109 amino acid domain near the C-terminus especially enriched (68/109 residues) in glutamate. This domain contained four repeats of a glutamate-rich 11 amino acid residue sequence (undecapeptide) and two repeats of a 26 amino acid peptide also rich in glutamic acid. Antibodies against a decamer corresponding to the undecapeptide from the glutamate rich region recognized a 65 kD protein in crude rod outer segment extracts. Northern analysis of poly A+ RNA from a variety of bovine tissues identified a 2.4 kb transcript only in the retina sample, suggesting that the expression may be retina-specific. More recently it was shown that garp is part of the 240 kD integral membrane protein complex that forms part of the cGMP-gated cation channel of bovine rod outer segments, thus identifing it as a third subunit (y) of the channel (2).
KeywordsPlexiform Layer Retinal Degeneration Bovine Retina Preimmune Seron cGMP Phosphodiesterase
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