Identifying the G protein, G z α

The signalling pathway associated with pertussis and cholera toxin sensitive G proteins have been extensively investigated. In contrast, the function and associated signal transduction cascade for the pertussis toxin insensitive G protein, G(Zα), have remained elusive. Therefore, the aim of this study was to identify the signal transduction pathway associated with G(Zα) by using the protein identification techniques of matrix assisted laser desorption ionization-time of flight mass spectroscopy and N-terminal Edman sequencing. We have chosen this technique to identify proteins that G(Zα) associates with and to gain insights into the potential role this G protein plays in cells. As G(Zα) is predominantly localized in neuronal tissues, homogenates of whole brain tissue were used. G(Zα) and its associated proteins were immunoprecipitated from brain tissue and identified. The immunoprecipitation of four proteins (140, 46, 41 and 36 kDa) was shown to be inhibited in the presence of the G (Zα) peptide. These proteins were subsequently identified as phospholipase C (PLC)-γ, β or γ-actin, G(Zα) and G(β), the β subunit of heterotrimeric G proteins, respectively. These results suggest that G(Zα) exists in a protein complex with the actin cytoskeleton and an important intracellular signalling enzyme, PLC-γ. These methods are powerful techniques for determining protein-protein interactions, and provide the first step to the identification of signalling proteins that G(Zα) associates with. However further experimentation will be required to determine the biological relevance of these protein interactions.</p