Regulation of the SNARE protein Ykt6 function by diprenylation and phosphorylation.

For proper intracellular vesicle transport, it is essential for transport vesicle membranes to fuse with the appropriate target membranes. Ykt6 is a SNARE protein with functions in diverse vesicle transport pathways, including secretory, endocytotic and autophagic pathways. To exert these functions, the association of Ykt6 with vesicle membranes and the change of its conformation from closed to open play key roles. Recent studies have revealed regulatory mechanisms involved in Ykt6 membrane association and conformation change. When in the cytosol, the vicinal cysteine residues within the C-terminal CCAIM sequence of Ykt6 undergo diprenylation (farnesylation of the distal cysteine residues by farnesyltransferase; this is followed by geranylgeranylation of the proximal cysteine residue by geranylgeranyltransferase-III). Phosphorylation of a serine residue within the SNARE domain triggers the conversion of the Ykt6 conformation from closed to open, allowing Ykt6 membrane association. In this commentary, I briefly summarize and discuss the recently revealed regulatory mechanisms of Ykt6 function by diprenylation and phosphorylation.