8.A.108. The Curature-stabilizing Protein YOP1 (YOP1) Family
The endoplasmic reticulum is a dynamic network of interconnected membrane tubules. Powers et al. 2017 reconstituted a dynamic tubular membrane network with purified endoplasmic reticulum proteins. Proteoliposomes containing the membrane-fusing GTPase Sey1p (1.N.5.1.6) and the curvature-stabilizing protein Yop1p from Saccharomyces cerevisiae formed a tubular network upon addition of GTP. The tubules rapidly fragment when GTP hydrolysis by Sey1p is inhibited, indicating that network maintenance requires continuous membrane fusion and that Yop1p favours the generation of highly curved membrane structures. Sey1p ( also forms networks with other curvature-stabilizing proteins, including reticulon and receptor expression-enhancing proteins (REEPs) from different species. Atlastin, the vertebrate orthologue of Sey1p, forms a GTP-hydrolysis-dependent network on its own, serving as both a fusion and curvature-stabilizing protein. These results show that organelle shape can be generated by a surprisingly small set of proteins and represents an energy-dependent steady state between formation and disassembly (Powers et al. 2017). Yop1 may function together with LNP1 (Sey1) (TC#s 8.A.109.1.1) to promote ER membrane fusion.