(75) Although the sugar-binding specificity of Fbs1 and Fbs2 is slightly different, Fbx proteins bind all glycoproteins that are translocated from the luminal side of the ER to the cytoplasm through recognition via OS-9 and/or XTP3-B (Fig.
ER-associated degradation of misfolded proteins via OS-9 and XTP3-B. After CNX and UGGT are released from the peptides, correctly folded proteins are transported to the Golgi.
When trimming of an outermost Man residue occurs on the C-arm of high mannose-type glycans by EDEM1 or EDEM3, it binds OS-9 and XTP3-B. These soluble intracellular lectins will guide the protein to the ubiquitin ligase complex, and glycoproteins having such glycans will be degraded by the proteasome (Fig.
(2010) Human XTP3-B binds to [alpha]1-antitrypsin variant null Hong Kong via the C-terminal MRH domain in a glycan-dependent manner.