Beta and gamma subunits of a yeast guanine nucleotide-binding protein are not essential for membrane association of the alpha subunit but are required for receptor coupling.
Proc Natl Acad Sci U S A
; 87(11): 4363-7, 1990 Jun.
Article
em En
| MEDLINE
| ID: mdl-2161538
ABSTRACT
Conditions were devised to demonstrate GTP-regulated coupling between the yeast STE2-encoded receptor and its cognate guanine nucleotide-binding protein (G protein). Treatment of partially purified membranes with guanosine 5'-[gamma-thio]triphosphate (GTP[gamma-S]) converted the receptor from a high-affinity state (Kd = 17 nM) to a much lower affinity state (Kd approximately 150 nM), as judged by three independent criteria rate of ligand (alpha-factor) dissociation, equilibrium binding, and antagonist competition. Expression of STE2 from the GAL1 promoter in MATa/MAT alpha diploids, which do not express GPA1 (encoding G protein alpha subunit, G alpha), STE4 (encoding G protein beta subunit, G beta), and STE18 (encoding G protein gamma subunit, G gamma) but do express another G protein alpha subunit (product of GPA2), yielded a single class of low-affinity receptors that were GTP[gamma-S]-insensitive, indicating that STE2 gene product cannot couple productively with other G proteins, even in the absence of competition by its cognate G protein. By using gpa1, STE4, and ste18 mutations, it was found that all three G protein subunits were required for functional coupling, as judged by the absence of high-affinity receptors when any of the three gene products was altered. This finding demonstrates that G beta and G gamma subunits are essential for formation of a productive complex between a G alpha subunit and its corresponding receptor. Wild-type STE4 and STE18 gene products were not essential for membrane localization of the GPA1 gene product, as indicated by cell fractionation and immunological analyses, suggesting that G beta and G gamma subunits interact with the receptor or make the G alpha subunit competent to associate correctly with the receptor, or both.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fatores de Transcrição
/
Transdução de Sinais
/
Receptores de Peptídeos
/
Receptores de Superfície Celular
/
Proteínas de Ligação ao GTP
Tipo de estudo:
Risk_factors_studies
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
1990
Tipo de documento:
Article