2mre
From Proteopedia
NMR structure of the Rad18-UBZ/ubiquitin complex
Structural highlights
FunctionUBC_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.[1] [2] Publication Abstract from PubMedUbiquitin-mediated interactions are critical for the cellular DNA damage response (DDR). Therefore, many DDR-related proteins contain ubiquitin-binding domains, including ubiquitin-binding zinc fingers (UBZs). The majority of these UBZ domains belong to the C2H2 (type 3 Poleta-like) or C2HC (type 4 Rad18-like) family. We have used nuclear magnetic resonance (NMR) spectroscopy to characterize the binding to ubiquitin and determine the structure of the type 4 UBZ domain (UBZ4) from human Rad18, which is a key ubiquitin ligase in the DNA damage tolerance pathway responsible for monoubiquitination of the DNA sliding clamp PCNA. The Rad18-UBZ domain binds ubiquitin with micromolar affinity and adopts a beta1-beta2-alpha fold similar to the previously characterized type 3 UBZ domain (UBZ3) from the translesion synthesis DNA polymerase Poleta. However, despite nearly identical structures, a disparity in the location of binding-induced NMR chemical shift perturbations shows that the Rad18-UBZ4 and Poleta-UBZ3 domains bind ubiquitin in distinctly different modes. The Rad18-UBZ4 domain interacts with ubiquitin with the alpha-helix and strand beta1 as shown by the structure of the Rad18-UBZ domain-ubiquitin complex determined in this work, while the Poleta-UBZ3 domain exclusively utilizes the alpha-helix. Our findings suggest the existence of two classes of UBZ domains in DDR-related proteins with similar structures but unique ubiquitin binding properties and provide context for further study to establish the differential roles of these domains in the complex cellular response to DNA damage. NMR Structure of the Human Rad18 Zinc Finger in Complex with Ubiquitin Defines a Class of UBZ Domains in Proteins Linked to the DNA Damage Response.,Rizzo AA, Salerno PE, Bezsonova I, Korzhnev DM Biochemistry. 2014 Sep 23;53(37):5895-906. doi: 10.1021/bi500823h. Epub 2014 Sep , 15. PMID:25162118[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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