FORMATION OF A YEAST SNARE COMPLEX IS ACCOMPANIED BY SIGNIFICANT STRUCTURAL-CHANGES

The evolutionarily conserved SNARE (SNAP receptor) proteins and their complexes are key players in the docking and fusion of secretory vesic les with their target membrane, Biophysical techniques were used to ch aracterize structural and energetic properties of the cytoplasmic doma ins of the yeast SNAREs Snc1 and Sso1, of the SNAP-25-like domain of S ec9. and of the Sso1:Sec9 and Sso1:Sec9:Snc1 complexes, Individually, all three SNAREs are monomeric; Sso1 shows significant secondary struc ture while Snc1 and Sec9 are largely unstructured, Ternary SNARE compl ex formation (K-D <50 nM) is accompanied by a more than two-fold incre ase in secondary structure, This binding induced structure, the large increase in thermal stability, and the self-association of the ternary complex: represent conserved properties of SNAREs that are probably i mportant in vesicle docking and fusion. (C) 1997 Federation of Europea n Biochemical Societies.