The N-terminal peptide of the syntaxin Tlg2p modulates binding of its closed conformation to Vps45p
Department of Biochemistry and Molecular Pharmacology
Binding, Competitive; Circular Dichroism; Electrophoretic Mobility Shift Assay; Immunoblotting; Kinetics; Models, Molecular; Mutation; Protein Binding; Protein Conformation; Protein Structure, Tertiary; Qa-SNARE Proteins; Recombinant Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Vesicular Transport Proteins
Life Sciences | Medicine and Health Sciences
The Sec1/Munc18 (SM) protein family regulates intracellular trafficking through interactions with individual SNARE proteins and assembled SNARE complexes. Revealing a common mechanism of this regulation has been challenging, largely because of the multiple modes of interaction observed between SM proteins and their cognate syntaxin-type SNAREs. These modes include binding of the SM to a closed conformation of syntaxin, binding to the N-terminal peptide of syntaxin, binding to assembled SNARE complexes, and/or binding to nonsyntaxin SNAREs. The SM protein Vps45p, which regulates endosomal trafficking in yeast, binds the conserved N-terminal peptide of the syntaxin Tlg2p. We used size exclusion chromatography and a quantitative fluorescent gel mobility shift assay to reveal an additional binding site that does not require the Tlg2p N-peptide. Characterization of Tlg2p mutants and truncations indicate that this binding site corresponds to a closed conformation of Tlg2p. Furthermore, the Tlg2p N-peptide competes with the closed conformation for binding, suggesting a fundamental regulatory mechanism for SM-syntaxin interactions in SNARE assembly and membrane fusion.
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Citation: Proc Natl Acad Sci U S A. 2009 Aug 25;106(34):14303-8. Epub 2009 Aug 10. Link to article on publisher's site