title: Mechanistic insight into the allosteric activation of a ubiquitin-conjugating enzyme by RING-type ubiquitin ligases.
abstract: Ubiquitin-conjugating enzymes (E2s) collaborate with the ubiquitin-activating enzyme (E1) and ubiquitin ligases (E3s) to attach ubiquitin to target proteins. RING-containing E3s simultaneously bind to E2s and substrates, bringing them into close proximity and thus facilitating ubiquitination. We show herein that, although the E3-binding site on the human E2 UbcH5b is distant from its active site, two RING-type minimal E3 modules lacking substrate-binding functions greatly stimulate the rate of ubiquitin release from the UbcH5b-ubiquitin thioester. Using statistical coupling analysis and mutagenesis, we identify and characterize clusters of coevolving and functionally linked residues within UbcH5b that span its E3-binding and active sites. Several UbcH5b mutants are defective in their stimulation by E3s despite their abilities to bind to these E3s, to form ubiquitin thioesters, and to release ubiquitin at a basal rate. One such mutation, I37A, is distant from both the active site and the E3-binding site of UbcH5b. Our studies reveal structural determinants for communication between distal functional sites of E2s and suggest that RING-type E3s activate E2s allosterically.
authors.affiliation: Department of Biochemistry and Pharmacology and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
authors.forename: Engin
authors.initials: E
authors.lastname: Ozkan
authors.forename: Hongtao
authors.initials: H
authors.lastname: Yu
authors.forename: Johann
authors.initials: J
authors.lastname: Deisenhofer
mesh_terms: D000495:Allosteric Site; D001665:Binding Sites; D016000:Cluster Analysis; D019926:Cyclin B / Q000737:chemistry; D056744:Cyclin B1; D003545:Cysteine / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D004952:Esters / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008025:Ligases / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D016296:Mutagenesis; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013997:Time Factors; D025801:Ubiquitin / Q000737:chemistry; D044764:Ubiquitin-Activating Enzymes / Q000737:chemistry; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry*; D043743:Ubiquitin-Protein Ligase Complexes / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry*
chemical_list: C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1; D004952:Esters; D010455:Peptides; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; D044764:Ubiquitin-Activating Enzymes; D003545:Cysteine