Cloning and characterization of three salamander retinalG-protein beta subunits

[摘要] Purpose: Recent evidence has shown that the beta-gamma dimers(bg) of activated heterotrimeric G-proteins are important inmany cellular signaling pathways. Since two distinct transducin alphasubunits have been cloned from the salamander retina, we aimed toidentify and characterize the G-protein beta (Gb) subunits that areinvolved in visual signal transduction in the salamander.Methods: A salamander retina cDNA library was screened usingdegenerate oligonucleotide primers designed from a compilation of knownGb sequences. Tissue specific expression was determined by reversetranscriptase PCR (RT-PCR).Results: The library screening resulted in the cloning of threefull-length sequences, two of which encode proteins of 340 residues andthe third being an iniation variant of 353 and 395 residues. Noidentical matches were found in GenBank but each shows highest homologyto G-beta-1 (b1), G-beta-3 (b3), and G-beta-5(b5 and b5L) subunits of other species,respectively. The b1 and b3 subunits are 84.7%identical to each other but both show only 52% identity to b5at the protein level. RT-PCR analysis showed that all the subunits areexpressed in multiple tissues, including the retina. However, theb5L splice variant was found only in the retina.Conclusions: Three distinct Gb subunit transcripts areexpressed in the salamander retina. These subunits have proven to beimportant in the visual system of mammalian models.

[学科分类] 生物化学/生物物理