The structural and functional homology of the beta and gamma subunit complexes from signal transducing GTP-binding proteins (G-proteins) will be examined. The proposed research is aimed at establishing the degree to which the beta gamma complexes from several purified G-proteins and the structurally distinct forms of beta gamma proteins have the identical functions. Two functional assays will be established to characterize the beta gamma proteins: 1. The enhancement of pertussis toxin-catalyzed ADP- ribosylation of resolved alpha subunits of Gt, Gi, and Go proteins; and 2. The regulation of the relative affinities of G-protein alpha subunits for GDP and GTP. The apparently distinct form of beta gamma protein, beta-35, will be partially sequenced for protease and CNBr fragments which are electrophoretically or immunologically distinct from those of the Gt beta subunit. The structures for the immunologically distinct gamma-peptides of rabbit liver Gi, human placental Gi, and bovine Go will be determined by molecular cloning of cDNAs. The participation of specific beta gamma protein(s) in the transductions of the G- protein mediated alpha-adrenergic inhibition of human platelet adenylyl cyclase, muscarinic activation of voltage-dependent potassium channels in isolated chick myocytes, and angiotensin II activation of phospholipase C of bovine adrenal cortex and rat hepatocytes will be probed using rabbit polyclonal antisera or affinity purified fractions therefrom. The interaction of beta gamma with a low molecular weight GTP-binding protein, Gp, will be investigated, in order to determine if two distinct classes of G- proteins exist characterized differentially by beta gamma interaction. Finally, a beta gamma affinity chromatography for interacting proteins will be developed to isolate them for identification of cellular function(s). This set of studies should allow for the evaluation, quantitatively and qualitatively, of existing hypotheses concerning the cellular function of the beta gamma subunits of signal transducing G-proteins.
| Mitchell, J; Northup, J K; Schimmer, B P (1992) Defective guanyl nucleotide-binding protein beta gamma subunits in a forskolin-resistant mutant of the Y1 adrenocortical cell line. Proc Natl Acad Sci U S A 89:8933-7 |
| Tamir, H; Fawzi, A B; Tamir, A et al. (1991) G-protein beta gamma forms: identity of beta and diversity of gamma subunits. Biochemistry 30:3929-36 |
| Fawzi, A B; Fay, D S; Murphy, E A et al. (1991) Rhodopsin and the retinal G-protein distinguish among G-protein beta gamma subunit forms. J Biol Chem 266:12194-200 |
| Tamir, A; Fawzi, A B; Northup, J K (1990) Unique guanine nucleotide binding properties of the human placental GTP-binding protein Gp. Biochemistry 29:6947-54 |
| Fawzi, A B; Northup, J K (1990) Guanine nucleotide binding characteristics of transducin: essential role of rhodopsin for rapid exchange of guanine nucleotides. Biochemistry 29:3804-12 |
