RING finger, H2 subclass, found in ubiquitin-protein ligase E3-alpha-1 (UBR1) and similar proteins
UBR1, also known as N-recognin-1 or E3alpha-I, is an E3 ubiquitin-protein ligase component of the N-end rule pathway. It also promotes degradation of proteins via distinct mechanism that detects a misfolded conformation. UBR1 associates with the RAD6-encoded E2 enzyme to form an E2-E3 complex that catalyzes the synthesis of a substrate-linked multi-ubiquitin chain and may also mediate the delivery of substrates to the 26S proteasome. Moreover, UBR1 promotes the degradation of misfolded proteins in the cytosol. It promotes protein kinase quality control and sensitizes cells to heat shock protein 90 (Hsp90) inhibition. Furthermore, UBR1 functions as a polyubiquitylation-enhancing component of the UBR1-UFD4 complex in its targeting of ubiquitin-fusion degradation (UFD) substrates. UBR1 harbors at least three distinct substrate-binding sites and functions in association with Ubc2/Rad6 and also Ubc4. It contains an N-terminal ubiquitin-recognin (UBR) box involved in binding type-1 (basic) N-end rule substrate, an N-domain (also known as ClpS domain) required for type-2 (bulky hydrophobic) N-end rule substrate recognition, a C3H2C3-type RING-H2 finger, and a C-terminal UBR-specific autoinhibitory (UAIN) domain. A missense mutation in UBR1 is responsible for Johanson-Blizzard syndrome leads to UBR box unfolding and loss of function.
Comment:C3H2C3-type RING-H2 finger consensus motif: C-X2-C-X(9-39)-C-X(1-3)-H-X(2-3)-H-X2-C-X(4-48)-C-X2-C, where X is any amino acid and the number of X residues varies in different fingers
Comment:A RING finger typically binds two zinc atoms, with its Cys and/or His side chains in a unique "cross-brace" arrangement.
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