E2 enzymes: more than just middle men

Stewart, Mark; Ritterhoff, Tobias; Klevit, Rachel E.; Brzović, Peter S.

doi:10.1038/cr.2016.35

Cited by 442 publications

(453 citation statements)

References 146 publications

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“…A similar hydrophobic tethering mechanism for the donor ubiquitin (or donor Ubl) promotes catalytic efficiency and processivity of E2 enzymes (Stewart et al, 2016) and was shown to be stabilized by RING-type E3 enzymes (Dou et al, 2012(Dou et al, , 2013Plechanovová et al, 2012;Pruneda et al, 2012;Scott et al, 2014;Branigan et al, 2015;Wright et al, 2016) as well as SUMO-ligases (Reverter and Lima, 2005;Cappadocia et al, 2015;Streich and Lima, 2016). Importantly, however, the interactions of HECT E3 or E2 enzymes with the donor ubiquitin do not determine the linkage specificity of ubiquitin chain formation.…”

Section: Positioning Of the Donor Ubiquitin On The Hect C-lobementioning

confidence: 99%

Structural mechanisms of HECT-type ubiquitin ligases

Lorenz

2017

Biological Chemistry

111

131

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Ubiquitin ligases (E3 enzymes) transfer ubiquitin from ubiquitin-conjugating (E2) enzymes to target proteins. By determining the selection of target proteins, modification sites on those target proteins, and the types of ubiquitin modifications that are formed, E3 enzymes are key specificity factors in ubiquitin signaling. Here, I summarize our knowledge of the structural mechanisms in the HECT E3 subfamily, many members of which play important roles in human disease. I discuss interactions of the conserved HECT domain with E2 enzymes, ubiquitin and target proteins, as well as macromolecular interactions with regulatory functions. While we understand individual steps in the catalytic cycle of HECT E3 enzymes on a structural level, this review also highlights key aspects that have yet to be elucidated. For instance, it remains unclear how diverse target proteins are presented to the catalytic center and how certain HECT E3 enzymes achieve specificity in ubiquitin linkage formation. The structural and functional properties of the N-terminal regions of HECT E3 enzymes that likely act as signaling hubs are also largely unknown. Structural insights into these aspects may open up routes for a therapeutic intervention with specific HECT E3 functions in distinct pathophysiological settings.

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Section: Positioning Of the Donor Ubiquitin On The Hect C-lobementioning

confidence: 99%

Structural mechanisms of HECT-type ubiquitin ligases

Lorenz

2017

Biological Chemistry

111

131

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“…The resulting E2 ~ Ub intermediate interacts with members of three different families of Ub E3 ligases (RING, HECT, and RING-in-between-RING (RBR)) that catalyze Ub conjugation to target proteins by distinct mechanisms 9–11 . The catalytic mechanism of RING E3s involves interactions between a zinc-binding RING domain and the E2 ~ Ub thioester intermediate that facilitates nucleophilic attack of the E2 ~ Ub thioester by a lysine on the target protein directly 9–11 . This contrasts with the mechanism of HECT E3s, which are structurally unrelated to RING E3s.…”

Section: Introductionmentioning

confidence: 99%

Structural insights into the mechanism and E2 specificity of the RBR E3 ubiquitin ligase HHARI

Yuan

Atkison

et al. 2017

Nat Commun

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RING-in-between-RING (RBR) ubiquitin (Ub) E3 ligases function with Ub E2s through a RING/HECT hybrid mechanism to conjugate Ub to target proteins. Here, we report the crystal structure of the RBR E3, HHARI, in complex with a UbcH7 ~ Ub thioester mimetic which reveals the molecular basis for the specificity of this cognate E2/RBR E3 pair. The structure also reveals mechanistically important conformational changes in the RING1 and UBA-like domains of HHARI that accompany UbcH7 ~ Ub binding and provides a molecular basis by which HHARI recruits E2 ~ Ub in an ‘open’ conformation. In addition to optimally functioning with an E2 that solely performs transthiolation, our data suggests that HHARI prevents spurious discharge of Ub from E2 to lysine residues by: (1) harboring structural elements that block E2 ~ Ub from adopting a ‘closed’ conformation and (2) participating in contacts to ubiquitin that promote an open E2 ~ Ub conformation.

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“…In unusual cases, ubiquitin can be linked to the free N-terminal amino group of a substrate or of ubiquitin, or even to serine or threonine side chains (forming ester bonds). In humans, there are two E1 enzymes and 32 E2s that are known to facilitate ubiquitin conjugation [1], while Saccharomyces cerevisiae has a single E1 and 11 E2s [2]. There are over 600 E3s encoded in the human genome and at least 51 in S. cerevisiae [2], and these enzymes collectively coordinate the ubiquitylation of thousands of substrates.…”

Section: Introductionmentioning

confidence: 99%

“…There are 14 human RBR E3s [5] and two in S. cerevisiae [1]. PARKIN, associated with the neurological condition Parkinson’s disease, is one of the best-studied RBR E3s [13].…”

Section: Introductionmentioning

confidence: 99%

Enzyme–substrate relationships in the ubiquitin system: approaches for identifying substrates of ubiquitin ligases

O'Connor

Huibregtse

2017

Cell. Mol. Life Sci.

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Protein ubiquitylation is an important post-translational modification, regulating aspects of virtually every biochemical pathway in eukaryotic cells. Hundreds of enzymes participate in the conjugation and deconjugation of ubiquitin, as well as the recognition, signaling functions, and degradation of ubiquitylated proteins. Regulation of ubiquitylation is most commonly at the level of recognition of substrates by E3 ubiquitin ligases. Characterization of the network of E3-substrate relationships is a major goal and challenge in the field, as this it expected to yield fundamental biological insights and opportunities for drug development. There has been remarkable success in identifying substrates for some E3 ligases, in many instances using standard protein-protein interaction techniques (e.g., two-hybrid screens, co-immunoprecipitations paired with mass spectrometry). However, some E3s have remained refractory to characterization, while others have simply not yet been studied due to the sheer number and diversity of E3s. This review will discuss the range of tools and techniques that can be used for substrate profiling of E3 ligases.

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E2 enzymes: more than just middle men

Cited by 442 publications

References 146 publications

Structural mechanisms of HECT-type ubiquitin ligases

Structural mechanisms of HECT-type ubiquitin ligases

Structural insights into the mechanism and E2 specificity of the RBR E3 ubiquitin ligase HHARI

Enzyme–substrate relationships in the ubiquitin system: approaches for identifying substrates of ubiquitin ligases

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