Substrate-recognition component of a Cul2-RING (CRL2) E3 ubiquitin-protein ligase complex of the DesCEND (destruction via C-end degrons) pathway, which recognizes a C-degron located at the extreme C terminus of target proteins, leading to their ubiquitination and degradation (By similarity). The C-degron recognized by the DesCEND pathway is usually a motif of less than ten residues and can be present in full-length proteins, truncated proteins or proteolytically cleaved forms (By similarity). The CRL2(FEM1B) complex specifically recognizes proteins ending with -Gly-Leu-Asp-Arg, such as CDK5R1, leading to their ubiquitination and degradation (By similarity). Also acts as a regulator of the reductive stress response by mediating ubiquitination of reduced FNIP1: in response to reductive stress, the CRL2(FEM1B) complex specifically recognizes a conserved Cys degron in FNIP1 when this degron is reduced, leading to FNIP1 degradation and subsequent activation of mitochondria to recalibrate reactive oxygen species (ROS) (PubMed:32941802). Promotes ubiquitination of GLI1, suppressing GLI1 transcriptional activator activity (By similarity). Promotes ubiquitination and degradation of ANKRD37 (PubMed:21723927). Promotes ubiquitination and degradation of SLBP (By similarity). Involved in apoptosis by acting as a death receptor-associated protein that mediates apoptosis (By similarity). Also involved in glucose homeostasis in pancreatic islet (PubMed:16024793). May also act as an adapter/mediator in replication stress-induced signaling that leads to the activation of CHEK1 (By similarity). Protein modification; protein ubiquitination. Component of a CRL2 E3 ubiquitin-protein ligase complex, also named ECS (Elongin BC-CUL2/5-SOCS-box protein) complex, composed of CUL2, Elongin BC (ELOB and ELOC), RBX1 and substrate-specific adapter FEM1B (PubMed:32941802). Homooligomer (By similarity). Interacts with PPM1F and PHTF1 (PubMed:15601915). Interacts with the death domain of FAS/TNFRSF6 and TNFRSF1A. Interacts with CHEK1 (By similarity). Interacts with NKX3-1 (PubMed:18816836). In the nucleus, the protein level increased slightly after camptothecin (CPT) treatment. Associated with chromatin. Expressed in pancreatic islets, within both beta cells and non-beta cells (at protein level) (PubMed:16024793). Highly expressed in adult testis; expressed in all types of spermatogonia (PubMed:9828124, PubMed:18816836). Also expressed in the prostate of neonatal mice (PubMed:18816836). Abnormal glucose tolerance predominantly due to defective glucose-stimulated insulin secretion (PubMed:16024793). Mice also show defects in prostate ductal morphogenesis and secretory protein expression (PubMed:18816836). Belongs to the fem-1 family.