Insights into the structure and molecular topography of the fatty acylated domain of synaptotagmin-1.

Abundant attention has focused on synaptotagmin's C2 domains, but less is known about the structure and function of its other regions. Here, we synthesized the N-acetylated, C-end amidated and Cys-palmitated peptide (VLTCCFCICK KCLFKKKNKK K) which includes the fatty acylated cysteine residues in the membrane-affiliated domain of synaptotagmin-1. Fourier-transform infrared spectrometry indicated that this peptide's conformation is influenced by environmental polarity. In artificial bilayer membranes, this peptide exhibited abundant β-structure. Electron microscopy revealed that this peptide also promoted the stacking of liposome membranes. Together these results suggest that the fatty acylated region of synaptotagmin-1 is likely to adopt β-structure in biological membranes. This preference for β-structure versus α-helix has functional implications for the role of synaptotagmin-1 in synaptic vesicle exocytosis.