Poxvirus K7 Protein Adopts a Bcl-2 Fold: Biochemical Mapping of Its Interactions with Human DEAD Box RNA Helicase DDX3

• Published in: Journal of molecular biology Vol. 385; no. 3; pp. 843 - 853
• Main Authors: Kalverda, Arnout P., Thompson, Gary S., Vogel, Andre, Schröder, Martina, Bowie, Andrew G., Khan, Amir R., Homans, Steve W.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 23.01.2009
• Subjects: Bcl-2; Chromatography, Gel; DDX3 helicase; DEAD-box RNA Helicases - metabolism; Humans; innate immunity; K7 protein; Magnetic Resonance Spectroscopy; nuclear magnetic resonance (NMR) spectroscopy; Orthopoxvirus; Poxviridae - metabolism; Poxvirus; Protein Binding; Vaccinia virus; Viral Proteins - metabolism; Bcl-2; NOE; rTEV; mRNA; nuclear magnetic resonance (NMR) spectroscopy; RDC; NF-κB; DDX3 helicase; innate immunity; IRAK2; VACV; TRAF6; TLR; HSQC; K7 protein
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2008.09.048

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 κB 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 α-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.