Critical Residues of Gβγ for the interaction with the SNARE Complex

The mechanisms and regulation of neurotransmitter release is a complex process involving many co-factors and proteins. One critical interaction is the regulation of exocytosis when G-protein {beta}{gamma} (G{beta}{gamma}) dimers bind to the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein complex. The complex is comprised of N-ethylmaleimide-sensitive factor attachment protein-25 (SNAP-25), syntaxin 1A, and synaptobrevin. Herein we probe across the entire family of human G{beta} and G{gamma} proteins for residues critical for the interaction with SNARE, by systematically screening peptide sequences for their ability to bind to tSNARE. The coiled-coil region of G{beta}{gamma} showed high affinity to tSNARE, along with the propeller region of G{beta} on the opposite side from the coiled-coil region. Peptides based on G{beta}1{gamma}2, shown to have high affinity to SNARE, tSNARE were screened further by alanine scanning to probe for residues critical for binding to tSNARE. Full length G{beta}1{gamma}2 and SNARE were docked computationally using Rosetta, to examine the experimentally determined binding sites. Docking converged on two possible sites of interaction using two distinct regions of both G{beta}1{gamma}2 and SNARE.