Single molecule mechanical probing of the SNARE protein interactions

¹ University of California
² University of Wisconsin

^* To whom correspondence should be addressed. E-mail: vlad{at}ucr.edu.

Submitted on August 24, 2005
Revised on November 23, 2005
Accepted on 11 April 2006

	Abstract

Exocytotic release of neurotransmitters is mediated by the ternary soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptors (SNAREs) complex, comprised of syntaxin (Sx), synaptosome-associated protein of 25 kDa (SNAP25) and synaptobrevin 2 (Sb2). Since exocytosis involves the non-equilibrium process of association and dissociation of bonds between molecules of the SNARE complex, dynamic measurements at the single molecule level are necessary for a detailed understanding of these interactions. To address this issue, we used the Atomic Force Microscope (AFM) in force spectroscopy mode to show from single molecule investigations of the SNARE complex, that Sx1A and Sb2 are zippered throughout their entire SNARE domains without the involvement of SNAP25. When SNAP25B is present in the complex, it creates a local interaction at the '0' (ionic) layer by cuffing Sx1A and Sb2. Force loading rate studies indicate that the ternary complex interaction is more stable than the Sx1A-Sb2 interaction.

Key Words: atomic force microscopy, exocytosis, force spectroscopy, nanomanipulation, single molecule measurements

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