2l0f
From Proteopedia
Solution NMR structure of human polymerase iota UBM2 (P692A mutant) in complex with ubiquitin
Structural highlights
FunctionRS27A_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] Ribosomal protein S27a is a component of the 40S subunit of the ribosome.[3] [4] Publication Abstract from PubMedCells have evolved mutagenic bypass mechanisms that prevent stalling of the replication machinery at DNA lesions. This process, translesion DNA synthesis (TLS), involves switching from high-fidelity DNA polymerases to specialized DNA polymerases that replicate through a variety of DNA lesions. In eukaryotes, polymerase switching during TLS is regulated by the DNA damage-triggered monoubiquitylation of PCNA. How the switch operates is unknown, but all TLS polymerases of the so-called Y-family possess PCNA and ubiquitin-binding domains that are important for their function. To gain insight into the structural mechanisms underlying the regulation of TLS by ubiquitylation, we have probed the interaction of ubiquitin with a conserved ubiquitin-binding motif (UBM2) of Y-family polymerase Poliota. Using NMR spectroscopy, we have determined the structure of a complex of human Poliota UBM2 and ubiquitin, revealing a novel ubiquitin recognition fold consisting of two alpha-helices separated by a central trans-proline residue conserved in all UBMs. We show that, different from the majority of ubiquitin complexes characterized to date, ubiquitin residue Ile44 only plays a modest role in the association of ubiquitin with Poliota UBM2. Instead, binding of UBM2 is centered on the recognition of Leu8 in ubiquitin, which is essential for the interaction. Structural Basis of Ubiquitin Recognition by Translesion Synthesis DNA Polymerase iota,Cui G, Benirschke RC, Tuan HF, Juranic N, Macura S, Botuyan MV, Mer G Biochemistry. 2010 Nov 30;49(47):10198-10207. Epub 2010 Nov 4. PMID:21049971[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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