An autoinhibitory mechanism for nonsyntaxin SNARE proteins revealed by thestructure of Ykt6p

Ykt6p is a nonsyntaxin SNARE implicated in multiple intracellular membrane trafficking steps. Here we present the structure of the NH2-terminal domain of Ykt6p (Ykt6pN, residues 1 to 140). The structure of Ykt6pN differed ent irety from that of syntaxin and resembled the overall fold of the actin reg ulatory protein, profilin. Like some syntaxins, Ykt6p adopted a folded back conformation in which Ykt6pN bound to its COOH-terminal core domain. The N H2-terminal domain plays an important biological rote in the function of Yk t6p, which in vitro studies revealed to include influencing the kinetics an d proper assembly of SNARE complexes.