Mvp1 promotes Vps1-mediated fission of SNX-BAR–coated retrograde carriers from the endosome. A retrograde tubule budding from an endosome is depicted. The tubule contains integral membrane cargo, Vps10, and is coated by retromer, retromer SNX-BARs (Vps5–Vps17 heterodimer), and Mvp1. Based on the narrow diameter of membrane tubes produced in vitro by human SNX8 (van Weering et al., 2012a), the orthologue of yeast Mvp1, the coated tubule will be constricted at sites where it is wrapped by Mvp1. The constrictions are preferential sites for Vps1 membrane association and oligomerization, leading to fission of the tubule at these sites and the production of retrograde transport carriers of heterogeneous size.