This is the C-terminal domain of DSC E3 ubiquitin ligase complex subunit 3 (Dsc3), which contains two transmembrane helices and a characteristic GFDRL sequence motif. Dsc3 is a component of the DSC E3 ubiquitin ligase complex (a Golgi-specific protein ubiquitination system) that functions in protein homeostasis under non-stress conditions, playing a role in protein quality control [1,2,3]. Yeast DSC E3 ubiquitin ligase complex is the homologue of Hrd1 E3 ligase complex from mammals, in which Dsc1, Dsc2 and Dsc3 corresponds to Hrd1, Der1, and Usa1, respectively. Dsc3 is a Herp-like protein that acts as a bridge between Dsc1 and Dsc2 for their interaction [4].

1: Identification of candidate substrates for the Golgi Tul1 E3 ligase using quantitative diGly proteomics in yeast. Tong Z, Kim MS, Pandey A, Espenshade PJ; Mol Cell Proteomics. 2014;13:2871-2882. PMID:25078903

2: Sorting of a multi-subunit ubiquitin ligase complex in the endolysosome system. Yang X, Arines FM, Zhang W, Li M; Elife. 2018; [Epub ahead of print] PMID:29355480

3: Endosome and Golgi-associated degradation (EGAD) of membrane proteins regulates sphingolipid metabolism. Schmidt O, Weyer Y, Baumann V, Widerin MA, Eising S, Angelova M, Schleiffer A, Kremser L, Lindner H, Peter M, Frohlich F, Teis D; EMBO J. 2019;38:e101433. PMID:31368600

4: Yeast SREBP cleavage activation requires the Golgi Dsc E3 ligase complex. Stewart EV, Nwosu CC, Tong Z, Roguev A, Cummins TD, Kim DU, Hayles J, Park HO, Hoe KL, Powell DW, Krogan NJ, Espenshade PJ; Mol Cell. 2011;42:160-171. PMID:21504829