A segment of the C-terminal half of the G-protein .31 subunit specifies its interaction with the γ4 subunit

Abstract

The β and γ subunits of the heterotrimeric guanine nucleotide binding (G protein) act as a dimer and directly regulate various signal transduction pathways. By using cotransfection assays, we tested the ability of several βγ combinations to activate inositol phospholipid-specific phospholipase C (PI-PLC)-β2. Our findings indicate that only βγ combinations that form dimers will activate PI-PLC-beta 2. Since G beta 1 interacts with Gγ1, while G beta 2 cannot, chimeras between Gβ1 and Gβ2 were used to identify the regions in beta 1 that determine its specific association with γ1. Our evidence demonstrates that a chimera between β2 and β1 that contains the C-terminal 173 amino acids of beta 1 can interact and activate PI-PLC-β2 with γ1. Chimeras that contain portions of the β1 C-terminal region display a weaker association with γ1. Furthermore, the contribution of each of these regions depends on the sequence context of each chimeric protein. However, the segment between residues 210 and 293 of β1 consistently plays a critical role in specifying association with γ1.

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