4lcd
From Proteopedia
Structure of an Rsp5xUbxSna3 complex: Mechanism of ubiquitin ligation and lysine prioritization by a HECT E3
Structural highlights
Function[RSP5_YEAST] E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Component of a RSP5 ubiquitin ligase complex which specifies polyubiquitination and intracellular trafficking of the general amino acid permease GAP1 as well as other cell surface proteins like GAP1, FUR4, MAL61, PMA1 and STE2. The RSP5-BUL1/2 complex is also necessary for the heat-shock element (HSE)-mediated gene expression, nitrogen starvation GLN3-dependent transcription, pressure-induced differential regulation of the two tryptophan permeases TAT1 and TAT2 and sorting efficiency into multivesicular bodies. Also acts on RBP1. Plays a role in tolerance to o-dinitrobenzene. Involved in actin cytoskeleton organization and dynamics. Ubiquitinates the LAS17-binding proteins LSB1 and PIN3/LSB2 without directing them for degradation and affects LAS17 levels in a SLA1-dependent and LSB1/2-independent manner.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [UBC_HUMAN] Ubiquitin exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in lysosomal degradation; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling.[13] [14] Publication Abstract from PubMedUbiquitination by HECT E3 enzymes regulates myriad processes, including tumor suppression, transcription, protein trafficking, and degradation. HECT E3s use a two-step mechanism to ligate ubiquitin to target proteins. The first step is guided by interactions between the catalytic HECT domain and the E2 approximately ubiquitin intermediate, which promote formation of a transient, thioester-bonded HECT approximately ubiquitin intermediate. Here we report that the second step of ligation is mediated by a distinct catalytic architecture established by both the HECT E3 and its covalently linked ubiquitin. The structure of a chemically trapped proxy for an E3 approximately ubiquitin-substrate intermediate reveals three-way interactions between ubiquitin and the bilobal HECT domain orienting the E3 approximately ubiquitin thioester bond for ligation, and restricting the location of the substrate-binding domain to prioritize target lysines for ubiquitination. The data allow visualization of an E2-to-E3-to-substrate ubiquitin transfer cascade, and show how HECT-specific ubiquitin interactions driving multiple reactions are repurposed by a major E3 conformational change to promote ligation. DOI:http://dx.doi.org/10.7554/eLife.00828.001. Mechanism of ubiquitin ligation and lysine prioritization by a HECT E3.,Kamadurai HB, Qiu Y, Deng A, Harrison JS, Macdonald C, Actis M, Rodrigues P, Miller DJ, Souphron J, Lewis SM, Kurinov I, Fujii N, Hammel M, Piper R, Kuhlman B, Schulman BA Elife. 2013 Aug 8;2:e00828. doi: 10.7554/eLife.00828. Print 2013. PMID:23936628[15] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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Categories: Baker's yeast | Human | Kamadurai, H B | Miller, D | Schulman, B A | Crosslink | E3 | Hect | Ligase | Ligase-protein binding complex | Maleimide | Nedd4 | Rsp5 | Sna3 | Thioester | Ubiquitin
