This family includes SRP-independent targeting protein 2 (SND2) from yeast and transmembrane protein 208 (TMEM208) from mammals. Both are localized to the endoplasmic reticulum (ER) [1, 2]. SND2 works together with SND1 and SND3 in an alternative targeting route to the ER [1]. TMEM208 regulates both ER stress and autophagy. It contains three predicted transmembrane regions [2]. SND2 also known as Env10 in Saccharomyces cerevisiae, and its homologue as Mug69 in Schizosaccharomyces pombe. They were identified as proteins involved in vacuolar processing and morphology [3] and meiosis [4], respectively.

1: The SND proteins constitute an alternative targeting route to the endoplasmic reticulum. Aviram N, Ast T, Costa EA, Arakel EC, Chuartzman SG, Jan CH, Hassdenteufel S, Dudek J, Jung M, Schorr S, Zimmermann R, Schwappach B, Weissman JS, Schuldiner M; Nature. 2016;540:134-138. PMID:27905431

2: Transmembrane protein 208: a novel ER-localized protein that regulates autophagy and ER stress. Zhao Y, Hu J, Miao G, Qu L, Wang Z, Li G, Lv P, Ma D, Chen Y; PLoS One. 2013;8:e64228. PMID:23691174

3: A genome-wide immunodetection screen in S. cerevisiae uncovers novel genes involved in lysosomal vacuole function and morphology. Ricarte F, Menjivar R, Chhun S, Soreta T, Oliveira L, Hsueh T, Serranilla M, Gharakhanian E; PLoS One. 2011;6:e23696. PMID:21912603

4: A large-scale screen in S. pombe identifies seven novel genes required for critical meiotic events. Martin-Castellanos C, Blanco M, Rozalen AE, Perez-Hidalgo L, Garcia AI, Conde F, Mata J, Ellermeier C, Davis L, San-Segundo P, Smith GR, Moreno S; Curr Biol. 2005;15:2056-2062. PMID:16303567