Structural highlights
Function
[L_CCHFI] Displays RNA-directed RNA polymerase, deubiquitinating and deISGylase activities. RNA-dependent RNA polymerase is responsible for replication and transcription of the viral RNA genome. The deubiquitinating activity cleaves both ubiquitinated and ISGylated products and may therefore regulate ubiquitin and ISG15 dependent innate immunity. [RS27A_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 PubMed
Crimean Congo hemorrhagic fever virus (CCHFV) is a deadly human pathogen that evades innate immune responses by efficiently interfering with antiviral signaling pathways mediated by NF-kappaB, IRF3, and IFNalpha/beta. These pathways rely on protein ubiquitination for their activation, and one outcome is the modification of proteins with the ubiquitin (Ub)-like modifier interferon-stimulated gene (ISG)15. CCHFV and related viruses encode a deubiquitinase (DUB) of the ovarian tumor (OTU) family, which unlike eukaryotic OTU DUBs also targets ISG15 modifications. Here we characterized the viral OTU domain of CCHFV (vOTU) biochemically and structurally, revealing that it hydrolyzes four out of six tested Ub linkages, but lacks activity against linear and K29-linked Ub chains. vOTU cleaved Ub and ISG15 with similar kinetics, and we were able to understand vOTU cross-reactivity at the molecular level from crystal structures of vOTU in complex with Ub and ISG15. An N-terminal extension in vOTU not present in eukaryotic OTU binds to the hydrophobic Ile44 patch of Ub, which results in a dramatically different Ub orientation compared to a eukaryotic OTU-Ub complex. The C-terminal Ub-like fold of ISG15 (ISG15-C) adopts an equivalent binding orientation. Interestingly, ISG15-C contains an additional second hydrophobic surface that is specifically contacted by vOTU. These subtle differences in Ub/ISG15 binding allowed the design of vOTU variants specific for either Ub or ISG15, which will be useful tools to understand the relative contribution of ubiquitination vs. ISGylation in viral infection. Furthermore, the crystal structures will allow structure-based design of antiviral agents targeting this enzyme.
Molecular basis for ubiquitin and ISG15 cross-reactivity in viral ovarian tumor domains.,Akutsu M, Ye Y, Virdee S, Chin JW, Komander D Proc Natl Acad Sci U S A. 2011 Feb 8;108(6):2228-33. Epub 2011 Jan 25. PMID:21266548[5]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Huang F, Kirkpatrick D, Jiang X, Gygi S, Sorkin A. Differential regulation of EGF receptor internalization and degradation by multiubiquitination within the kinase domain. Mol Cell. 2006 Mar 17;21(6):737-48. PMID:16543144 doi:S1097-2765(06)00120-1
- ↑ Komander D. The emerging complexity of protein ubiquitination. Biochem Soc Trans. 2009 Oct;37(Pt 5):937-53. doi: 10.1042/BST0370937. PMID:19754430 doi:10.1042/BST0370937
- ↑ Huang F, Kirkpatrick D, Jiang X, Gygi S, Sorkin A. Differential regulation of EGF receptor internalization and degradation by multiubiquitination within the kinase domain. Mol Cell. 2006 Mar 17;21(6):737-48. PMID:16543144 doi:S1097-2765(06)00120-1
- ↑ Komander D. The emerging complexity of protein ubiquitination. Biochem Soc Trans. 2009 Oct;37(Pt 5):937-53. doi: 10.1042/BST0370937. PMID:19754430 doi:10.1042/BST0370937
- ↑ Akutsu M, Ye Y, Virdee S, Chin JW, Komander D. Molecular basis for ubiquitin and ISG15 cross-reactivity in viral ovarian tumor domains. Proc Natl Acad Sci U S A. 2011 Feb 8;108(6):2228-33. Epub 2011 Jan 25. PMID:21266548 doi:10.1073/pnas.1015287108
