2ybf
From Proteopedia
Complex of Rad18 (Rad6 binding domain) with Rad6b
Structural highlights
FunctionUBE2B_HUMAN Accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. In association with the E3 enzyme BRE1 (RNF20 and/or RNF40), it plays a role in transcription regulation by catalyzing the monoubiquitination of histone H2B at 'Lys-120' to form H2BK120ub1. H2BK120ub1 gives a specific tag for epigenetic transcriptional activation, elongation by RNA polymerase II, telomeric silencing, and is also a prerequisite for H3K4me and H3K79me formation. In vitro catalyzes 'Lys-11'-, as well as 'Lys-48'- and 'Lys-63'-linked polyubiquitination. Required for postreplication repair of UV-damaged DNA. Associates to the E3 ligase RAD18 to form the UBE2B-RAD18 ubiquitin ligase complex involved in mono-ubiquitination of DNA-associated PCNA on 'Lys-164'. May be involved in neurite outgrowth.[1] [2] [3] [4] [5] Publication Abstract from PubMedIn ubiquitin conjugation, different combinations of E2 and E3 enzymes catalyse either monoubiquitination or ubiquitin chain formation. The E2/E3 complex Rad6/Rad18 exclusively monoubiquitinates the proliferating cell nuclear antigen (PCNA) to signal for "error prone" DNA damage tolerance, whereas a different set of conjugation enzymes is required for ubiquitin chain formation on PCNA. Here we show that human E2 enzyme Rad6b is intrinsically capable of catalyzing ubiquitin chain formation. This activity is prevented during PCNA ubiquitination by the interaction of Rad6 with E3 enzyme Rad18. Using NMR and X-ray crystallography we show that the R6BD of Rad18 inhibits this activity by competing with ubiquitin for a noncovalent "backside" binding site on Rad6. Our findings provide mechanistic insights into how E3 enzymes can regulate the ubiquitin conjugation process. E3 ligase Rad18 promotes monoubiquitination rather than ubiquitin chain formation by E2 enzyme Rad6.,Hibbert RG, Huang A, Boelens R, Sixma TK Proc Natl Acad Sci U S A. 2011 Apr 5;108(14):5590-5. Epub 2011 Mar 21. PMID:21422291[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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