Ubiquitin regulatory domain X (UBX) found in UBX domain protein 1 (UBXN1) and similar proteins
UBXN1, also termed SAPK substrate protein 1 (SAKS1), UBA/UBX 33.3 kDa protein (Y33K), or UBXD10, is a widely expressed protein containing an N-terminal ubiquitin-associated (UBA) domain, a coiled-coil region, and a C-terminal ubiquitin-like (Ubl or UBX) domain that has a beta-grasp ubiquitin-like fold without the C-terminal double glycine motif. UBXN1 has been identified as a substrate for stress-activated protein kinases (SAPKs). It binds polyubiquitin and valosin-containing protein (VCP), suggesting a role as an adaptor that directs VCP to polyubiquitinated proteins facilitating its destruction by the proteasome. In addition, UBXN1 specifically binds to Homer2b. It may also interact with ubiquitin (Ub) and be involved in the Ub-proteasome proteolytic pathways. UBXN1 can also associate with autoubiquitinated BRCA1 tumor suppressor and inhibit its enzymatic function through its UBA domains.
Comment:3 (K6/R, K27/R, K48 Ub numbering) of the 7 lysines involved in chain linkage in ubiquitin (K6, K11, K27, K29, K33, K48, or K63, Ub numbering) are conserved in most members of this family; may have roles other than chain linkage
Jiyao W et al.(2023). "The conserved domain database in 2023.",