A non-zipper-like tetrameric coiled coil promotes membrane fusion
Tingting Zheng, Monica Bulacu, Geert Daudey, Frank Versluis, Jens Voskuhl, Giuliana Martelli, Jan Raap, G. J. Agur Sevink, Alexander Kros, Aimee L. Boyle
Two peptides, Coil-K and Coil-E, form a parallel heterodimeric coiled coil, CC-K/E, and have been shown to promote membrane fusion. This article examines the effects of reversing the sequence of Coil-E (to yield Coil-Er), on coiled-coil formation and membrane fusion. Coiled-coil assembly was studied using circular dichroism spectroscopy, paramagnetic proton NMR, fluorescence spectroscopy, analytical ultracentrifugation and computational simulations. Combined, the data show that Coil-K and Coil-Er combine in a 1[thin space (1/6-em)]:[thin space (1/6-em)]1 ratio to form an antiparallel tetramer, reinforcing previous studies that show small changes to peptide sequences strongly affect the stoichiometry and orientation of the resulting assemblies. Cholesterol-modified Coil-K and Coil-Er variants were subsequently tested for their ability to promote membrane fusion and the results were compared to the CC-K/E model system. Surprisingly, no significant differences were found between the two systems, despite the Coil-K/Er complex being ‘non-zipper-like’.
Circular dichroism, Secondary structure, Vesicle interactions, Biochemistry