title: Essentiality of a non-RING element in priming donor ubiquitin for catalysis by a monomeric E3.
abstract: RING E3 ligases catalyze the transfer of ubiquitin (Ub) from E2 ubiquitin-conjugating enzyme thioesterified with Ub (E2~Ub) to substrate. For RING E3 dimers, the RING domain of one subunit and tail of the second cooperate to prime Ub, but how this is accomplished by monomeric RING E3s in the absence of a tail-like component is currently unknown. Here, we present a crystal structure of a monomeric RING E3, Tyr363-phosphorylated human CBL-B, bound to a stabilized Ub-linked E2, revealing a similar mechanism in activating E2~Ub. Both pTyr363 and the pTyr363-induced element interact directly with Ub's Ile36 surface, improving the catalytic efficiency of Ub transfer by ~200-fold. Hence, interactions outside the canonical RING domain are crucial for optimizing Ub transfer in both monomeric and dimeric RING E3s. We propose that an additional non-RING Ub-priming element may be a common RING E3 feature.
authors.affiliation: The Beatson Institute for Cancer Research, Glasgow, United Kingdom.
authors.forename: Hao
authors.initials: H
authors.lastname: Dou
authors.affiliation: The Beatson Institute for Cancer Research, Glasgow, United Kingdom.
authors.forename: Lori
authors.initials: L
authors.lastname: Buetow
authors.affiliation: The Beatson Institute for Cancer Research, Glasgow, United Kingdom.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Sibbet
authors.affiliation: The Beatson Institute for Cancer Research, Glasgow, United Kingdom.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Cameron
authors.affiliation: The Beatson Institute for Cancer Research, Glasgow, United Kingdom.
authors.forename: Danny T
authors.initials: DT
authors.lastname: Huang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D003460:Crystallization; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation; D050721:Proto-Oncogene Proteins c-cbl / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; C492211:CBLB protein, human; D050721:Proto-Oncogene Proteins c-cbl