3chm
From Proteopedia
Crystal structure of PCI domain from A. thaliana COP9 signalosome subunit 7 (CSN7)
Structural highlights
Function[CSN7_ARATH] Component of the COP9 signalosome complex (CSN), a complex involved in various cellular and developmental processes such as photomorphogenesis and auxin and jasmonate responses. The CSN complex is an essential regulator of the ubiquitin (Ubl) conjugation pathway by mediating the deneddylation of the cullin subunits of SCF-type E3 ligase complexes, leading to decrease the Ubl ligase activity of SCF. It is involved in repression of photomorphogenesis in darkness by regulating the activity of COP1-containing Ubl ligase complexes. The complex is also required for degradation of IAA6 by regulating the activity of the Ubl ligase SCF-TIR complex.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe COP9 Signalosome (CSN) is a multiprotein complex that was originally identified in Arabidopsis thaliana as a negative regulator of photomorphogenesis and subsequently shown to be a general eukaryotic regulator of developmental signaling. The CSN plays various roles, but it has been most often implicated in regulating protein degradation pathways. Six of eight CSN subunits bear a sequence motif called PCI. Here, we report studies of subunit 7 (CSN7) from Arabidopsis, which contains such a motif. Our in vitro and structural results, based on 1.5 A crystallographic data, enable a definition of a PCI domain, built from helical bundle and winged helix subdomains. Using functional binding assays, we demonstrate that the PCI domain (residues 1 to 169) interacts with two other PCI proteins, CSN8 and CSN1. CSN7 interactions with CSN8 use both PCI subdomains. Furthermore, we show that a C-terminal tail outside of this PCI domain is responsible for association with the non-PCI subunit, CSN6. In vivo studies of transgenic plants revealed that the overexpressed CSN7 PCI domain does not assemble into the CSN, nor can it complement a null mutation of CSN7. However, a CSN7 clone that contains the PCI domain plus part of the CSN6 binding domain can complement the null mutation in terms of seedling viability and photomorphogenesis. These transgenic plants, though, are defective in adult growth, suggesting that the CSN7 C-terminal tail plays additional functional roles. Together, the findings have implications for CSN assembly and function, highlighting necessary interactions between subunits. The Arabidopsis COP9 signalosome subunit 7 is a model PCI domain protein with subdomains involved in COP9 signalosome assembly.,Dessau M, Halimi Y, Erez T, Chomsky-Hecht O, Chamovitz DA, Hirsch JA Plant Cell. 2008 Oct;20(10):2815-34. Epub 2008 Oct 14. PMID:18854373[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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