Critical Residues of Gβγ for the interaction with the SNARE Complex

Abstract

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 Gprotein βγ (Gβγ) 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 Gβ and Gγ 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 Gβγ showed high affinity to tSNARE, along with the propeller region of Gβ on the opposite side from the coiled-coil region. Peptides based on Gβ 1 γ 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 Gβ 1 γ 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 Gβ 1 γ 2 and SNARE.

Specificities of Gβγ subunits for the SNARE complex before and after stimulation of α 2a -adrenergic receptors

“…The main molecular mechanisms behind the binding selectivity between various Gs and their effectors are still unknown. However, ongoing investigations of interactions between each G subunit and t-SNARE are suggestive of the importance of charged residues in this process (49).…”

Specificity of Gβ and γ subunits to the SNARE complex both at rest and after α2aadrenergic receptor stimulation

“…The main molecular mechanisms behind binding selectivity between various Gβγs and their effectors are still unknown. However, ongoing investigations of interactions between each Gγ and t-SNARE are suggesting the importance of charged residues during this process( 48 ).…”