Lectin involved in the quality control of the secretory pathway. As a member of the endoplasmic reticulum-associated degradation lumenal (ERAD-L) surveillance system, targets misfolded endoplasmic reticulum lumenal glycoproteins for degradation. The recognition of targets is N-glycan specific. Functions in recruiting misfolded protein substrates in conjunction with HRD3 (PubMed:32327568). Homodimer (PubMed:22262864). Component of the HRD1 ubiquitin ligase complex which contains the E3 ligase HRD1, its cofactors HRD3, USA1 and DER1, substrate recruiting factor YOS9 and CDC48-binding protein UBX2 (PubMed:16873065, PubMed:16873066). Within the complex, interacts (via N-terminus) with HRD3 (PubMed:22262864). In ERAD-L, HRD3 and YOS9 jointly bind misfolded glycoproteins in the endoplasmic reticulum (ER) lumen (PubMed:32327568). Movement of ERAD-L substrates through the ER membrane is facilitated by HRD1 and DER1 which have lateral gates facing each other and which distort the membrane region between the lateral gates, making it much thinner than a normal phospholipid bilayer (PubMed:32327568). Substrates insert into the membrane as a hairpin loop with one strand interacting with DER1 and the other with HRD1 (PubMed:32327568). The HRD1 complex interacts with the heterotrimeric CDC48-NPL4-UFD1 ATPase complex which is recruited by UBX2 via its interaction with CDC48 and which moves ubiquitinated substrates to the cytosol for targeting to the proteasome (PubMed:16873065, PubMed:16873066). Interacts with KAR2 and EMP47 (PubMed:16873065). Interacts with misfolded ER lumenal proteins like PCR1 (PubMed:16168370, PubMed:16168371, PubMed:16168372). Interacts with the GPI-anchored proteins GAS1 and MKC7 (PubMed:12077121). The MRH (mannose 6-phosphate receptor homology) domain is required for the ERAD-L activity. Interaction of substrate with HRD1 is reduced; in YOS9 and USA1 double mutants this interaction is completely abolished. Interaction of substrate (either glycosylated or non-glycosylated) with HRD3 is not affected. Belongs to the OS-9 family.