Novel Interacting Mode Between Ent3-ENTH And The SNARE Vti1p-Habc

In accordance with their key role in membrane fusion of vesicle transport, the SNARE proteins are always regarded as a special cargo which has to be correctly packed into the vesicles during the budding process. However, the mechanism of how the SNARE proteins being recognized during budding process is less known. Here, we solved the crystal structures of yeast Vti1p-Habc and Ent3p-ENTH separately and found that though they all share the conserved tertiary structure as their mammalian homologue; the supposed interacting surfaces were different from that of the mammalian Vti1b and EpsinR. Then we solved the crystal structure of the Habc domain of Vti1p and the ENTH domain of Ent3p and found that the yeast Vti1p-Habc binds with the opposite side of the 3 helix bundle compared to its mammalian homologue. Two-hybrid experiments further confirmed this novel binding site in yeast. The complex structure shows a distinct binding model between the ENTH domain and Habc domain, and may have implications for the different sorting mechanism. Besides, our results may implicate that during evolution the Vti1 protein differentiated into two paralogues– one can bind the ENTH domain and one can not.