title: A small multigene family encodes Gi signal-transduction proteins.
abstract: The guanine nucleotide-binding regulatory proteins known as G proteins are receptor-associated signal-transduction molecules that are implicated in the control of a variety of metabolic processes. Recent evidence suggests that G proteins may mediate B-lymphocyte responses to bacterial lipopolysaccharide and may also transduce signals from the T-cell antigen receptor. Since these receptors are uniquely expressed on lymphoid cells, we used molecular cloning strategies to ask whether lymphocytes contain specialized G-protein alpha subunits to assist in signal transduction. Comparison of our two deduced human alpha i amino acid sequences with those previously determined for bovine and rodent G proteins permits the identification of three closely related but distinct types of alpha i molecules that comprise a small multigene family. Using gene-specific probes, we found that both of our alpha i genes are expressed in most cell types but in differing ratios. Our data support the view that a modest repertoire of extremely closely related G proteins mediates the transduction of signals derived from multiple different receptor molecules.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle / Q000235:genetics; D004247:DNA / Q000235:genetics; D004274:DNA, Recombinant; D019204:GTP-Binding Proteins / Q000235:genetics*; D005796:Genes; D006801:Humans; D008214:Lymphocytes / Q000032:analysis; D051379:Mice / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D051381:Rats / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004274:DNA, Recombinant; D004247:DNA; D019204:GTP-Binding Proteins