[Localization of antigenic sites for monoclonal antibodies against alpha-subunit of Go-protein from the bovine brain].

The properties of monoclonal antibodies (MA) specifically raised against the alpha-subunit of the GTP-binding protein from bovine brain, G0, were studied. The hybridoma clones were found to secrete MA capable to interact with different antigenic sites of G0 alpha. Clone 1D2 MA interacted with the N-terminal domain of G0 alpha. The antigenic sites for clones 3DE. 1H6 and 2E3 MA were localized in the C-terminal domain of the protein molecule. Using clone 1H6 MA, the site of G0 alpha involved in the interaction with the beta gamma complex located in the C-terminal domain of the alpha-subunit, was revealed. It was found that the interaction of the alpha-subunit with the beta gamma complex changed the conformation of the C-terminal fragment of G0 alpha (Mr5000) together with an increase in the alpha-subunit affinity for clone 2E3 MA. It was concluded that the observed conformational changes may be the reason for the increased affinity of the alpha-subunit for the receptor.