Cloning and characterization of three salamander retinal G-protein beta subunits.
OBJECTIVE
Recent evidence has shown that the beta-gamma dimers (beta gamma) of activated heterotrimeric G-proteins are important in many cellular signaling pathways. Since two distinct transducin alpha subunits have been cloned from the salamander retina, we aimed to identify and characterize the G-protein beta (Gbeta) subunits that are involved in visual signal transduction in the salamander.


METHODS
A salamander retina cDNA library was screened using degenerate oligonucleotide primers designed from a compilation of known Gbeta sequences. Tissue specific expression was determined by reverse transcriptase PCR (RT-PCR).


RESULTS
The library screening resulted in the cloning of three full-length sequences, two of which encode proteins of 340 residues and the third being an iniation variant of 353 and 395 residues. No identical matches were found in GenBank but each shows highest homology to G-beta-1 (beta1), G-beta-3 (beta3), and G-beta-5 (beta5 and beta5L) subunits of other species, respectively. The beta1 and beta3 subunits are 84.7% identical to each other but both show only 52% identity to beta5 at the protein level. RT-PCR analysis showed that all the subunits are expressed in multiple tissues, including the retina. However, the beta5L splice variant was found only in the retina.


CONCLUSIONS
Three distinct Gbeta subunit transcripts are expressed in the salamander retina. These subunits have proven to be important in the visual system of mammalian models.
Ryan
J C
JC
Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29403, USA. jcryan@miami.edu
Crouch
R K
RK
Ma
J X
JX
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000032:analysis; D005136:Eye Proteins / Q000032:analysis / Q000235:genetics*; D015723:Gene Library; D020962:Heterotrimeric GTP-Binding Proteins / Q000032:analysis / Q000235:genetics*; D008969:Molecular Sequence Data; D012160:Retina / Q000737:chemistry*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014562:Caudata / Q000235:genetics*; D014785:Vision, Ocular / Q000502:physiology
D017931:DNA Primers; D018076:DNA, Complementary; D005136:Eye Proteins; D020962:Heterotrimeric GTP-Binding Proteins