Poxvirus K7 protein adopts a Bcl-2 fold: biochemical mapping of its interactions with human DEAD box RNA helicase DDX3.
Poxviruses have evolved numerous strategies to evade host innate immunity. Vaccinia virus K7 is a 149-residue protein with previously unknown structure that is highly conserved in the orthopoxvirus family. K7 bears sequence and functional similarities to A52, which interacts with interleukin receptor-associated kinase 2 and tumor necrosis factor receptor-associated factor 6 to suppress nuclear factor kappaB activation and to stimulate the secretion of the anti-inflammatory cytokine interleukin-10. In contrast to A52, K7 forms a complex with DEAD box RNA helicase DDX3, thereby suppressing DDX3-mediated ifnb promoter induction. We determined the NMR solution structure of K7 to provide insight into the structural basis for poxvirus antagonism of innate immune signaling. The structure reveals an alpha-helical fold belonging to the Bcl-2 family despite an unrelated primary sequence. NMR chemical-shift mapping studies have localized the binding surface for DDX3 on a negatively charged face of K7. Furthermore, thermodynamic studies have mapped the K7-binding region to a 30-residue N-terminal fragment of DDX3, ahead of the core RNA helicase domains.
Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
Arnout P
AP
Kalverda
Gary S
GS
Thompson
Andre
A
Vogel
Martina
M
Schröder
Andrew G
AG
Bowie
Amir R
AR
Khan
Steve W
SW
Homans
D002850:Chromatography, Gel; D053487:DEAD-box RNA Helicases / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D011212:Poxviridae / Q000378:metabolism*; D011485:Protein Binding; D014764:Viral Proteins / Q000378:metabolism*
D014764:Viral Proteins; C119332:DDX3X protein, human; D053487:DEAD-box RNA Helicases