Structural highlights
Publication Abstract from PubMedThe Flavivirus nonstructural protein 1 (NS1) is a conserved, membrane-associated and secreted glycoprotein with replication and immune evasion functions. Secreted NS1 is a hexameric, barrel-shaped lipoprotein that can bind back to the plasma membrane of cells. Antibodies targeting cell surface-associated NS1 can be protective in vivo in a manner dependent on Fc effector functions. We describe here the crystal structure of a C-terminal fragment (residues 172-352) of West Nile (WNV) and Dengue virus NS1 proteins at 1.85 and 2.7 A resolution, respectively. NS1172-352 assembles as a unique rod-shaped dimer composed of a 16-stranded beta-platform flanked on one face by protruding connecting loops. We also determined the 3.0 A resolution structure of WNV NS1172-352 with the protective 22NS1 antibody Fab, which engages the loop-face of the rod. The head-to-head NS1172-352 dimer we observe in crystal lattices is supported by multiangle light and small-angle X-ray scattering studies. We used the available cryo-electron microscopy reconstruction to develop a pseudoatomic model of the NS1 hexamer. The model was constructed with the NS1172-352 dimeric rod aligned with the long axis of the barrel, and with the loop-face oriented away from the core. Difference densities suggest that the N-terminal region of NS1 forms globular lobes that mediate lateral contacts between dimers in the hexamer. Our model also suggests that the N-terminal lobe forms the surface of the central cavity where lipid binding may occur. Structural basis of Flavivirus NS1 assembly and antibody recognition.,Edeling MA, Diamond MS, Fremont DH Proc Natl Acad Sci U S A. 2014 Mar 4. PMID:24594604[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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