An autoinhibitory mechanism for nonsyntaxin SNARE proteins revealed by the structure 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 entirely from that of syntaxin and resembled the overall fold of the actin regulatory protein, profilin. Like some syntaxins, Ykt6p adopted a folded back conformation in which Ykt6pN bound to its COOH-terminal core domain. The NH₂-terminal domain plays an important biological role in the function of Ykt6p, which in vitro studies revealed to include influencing the kinetics and proper assembly of SNARE complexes.