Multimodal activation of the ubiquitin ligase SCF by Nedd8 conjugation.
Conjugation of ubiquitin-like protein Nedd8 to cullins (neddylation) is essential for the function of cullin-RING ubiquitin ligases (CRLs). Here, we show that neddylation stimulates CRL activity by multiple mechanisms. For the initiator ubiquitin, the major effect is to bridge the approximately 50 A gap between naked substrate and E2 approximately Ub bound to SCF. The gap between the acceptor lysine of ubiquitinated substrate and E2 approximately Ub is much smaller, and, consequentially, the impact of neddylation on transfer of subsequent ubiquitins by Cdc34 arises primarily from improved E2 recruitment and enhanced amide bond formation in the E2 active site. The combined effects of neddylation greatly enhance the probability that a substrate molecule acquires >or= 4 ubiquitins in a single encounter with a CRL. The surprisingly diverse effects of Nedd8 conjugation underscore the complexity of CRL regulation and suggest that modification of other ubiquitin ligases with ubiquitin or ubiquitin-like proteins may likewise have major functional consequences.
Howard Hughes Medical Institute, Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.
Anjanabha
A
Saha
Raymond J
RJ
Deshaies
D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D004789:Enzyme Activation; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D000075687:NEDD8 Protein; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*; D013379:Substrate Specificity; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism; D054875:Ubiquitination; D014452:Ubiquitins / Q000378:metabolism*; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
C495270:CTNNB1 protein, human; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D014452:Ubiquitins; D051176:beta Catenin; C577447:CDC34 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044843:SKP Cullin F-Box Protein Ligases