Identification of a GTP-binding protein alpha subunit that lacks an apparent ADP-ribosylation site for pertussis toxin
Recent molecular cloning of cDNA for the alpha subunit of bovine transducin (a guanine nucleotide-binding regulatory protein, or G protein) has revealed the presence of two retinal-specific transducins, called Tr and Tc, which are expressed in rod or cone photoreceptor cells. In a further study of G-protein diversity and signal transduction in the retina, we have identified a G-protein alpha subunit, which we refer to as Gz alpha, by isolating a human retinal cDNA clone that cross-hybridizes at reduced stringency with bovine Tr alpha-subunit cDNA. The deduced amino acid sequence of Gz alpha is 41-67% identical with those of other known G-protein alpha subunits. However, the 355-residue Gz alpha lacks a consensus site for ADP-ribosylation by pertussis toxin, and its amino acid sequence varies within a number of regions that are strongly conserved among all of the other G-protein alpha subunits. We suggest that Gz alpha, which appears to be highly expressed in neural tissues, represents a member of a subfamily of G proteins that mediate signal transduction in pertussis toxin-insensitive systems.
Additional Information© 1988 by the National Academy of Sciences. Contributed by Melvin I. Simon, January 14, 1988. We thank Drs. M. A. Lochrie, R. S. Miake-Lye, and B. W. Birren for materials and helpful advice; R. R. Reed for rat G alpha cDNA clones; J. Nathans for the human retinal cDNA library; and S. Horvath for synthesis of oligonucleotides. This work was supported by National Institutes of Health Grant GM34236. This sequence is being deposited in the EMBL/GenBank data base (Intelligenetics, Mountain View, CA, and Eur. Mol. Biol. Lab., Heidelberg) (accession no. J03260). The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Published - FONpnas88.pdf