title: Identification of a GTP-binding protein alpha subunit that lacks an apparent ADP-ribosylation site for pertussis toxin.
abstract: 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.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis; D019204:GTP-Binding Proteins / Q000032:analysis*; D006801:Humans; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D037342:Pertussis Toxin; D012333:RNA, Messenger / Q000032:analysis; D010566:Virulence Factors, Bordetella / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D004247:DNA; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins