Required for fusion of ER-derived vesicles with the Golgi during ER-to-Golgi protein transport. May be involved in proper membrane localization of Rab GTPases (By similarity). Component of the yip1-yif1 complex, composed of at least yif1, yip1 and yos1. The complex interacts with the ER to Golgi SNAREs bos1 and sec22 (By similarity). Belongs to the YIF1 family.