PMID: 22031945

Authors:

Hansman GS, Shahzad-Ul-Hussan S, McLellan JS, Chuang GY, Georgiev I, Shimoike T, Katayama K, Bewley CA, Kwong PD

Title:

Structural basis for norovirus inhibition and fucose mimicry by citrate.

Journal:

J Virol. 2011 Oct 26.

Abstract:

Human noroviruses bind with their capsid-protruding domains to histo-blood-group antigens (HBGAs), an interaction thought to direct their entry into cells. Although human noroviruses are the major cause of gastroenteritis outbreaks, development of antivirals has been lacking, mainly because human noroviruses cannot be cultivated. Here we use X-ray crystallography and saturation transfer difference (STD) NMR to analyze the interaction of citrate with genogroup II (GII) noroviruses. Crystals of citrate in complex with the protruding domain from norovirus GII.10 Vietnam026 diffracted to 1.4-A and showed a single citrate bound at the site of HBGA interaction. The citrate interaction was coordinated with an almost identical set of capsid interactions as involved in recognizing the terminal HBGA fucose, the saccharide which forms the primary conserved interaction between HBGAs and GII noroviruses. Citrate and a water molecule formed a ring-like structure that mimicked the pyranoside ring of fucose. STD NMR showed the protruding domain to have weak affinity for citrate (460 muM). This affinity, however, was similar to the affinities of the protruding domain for fucose (460 muM) and H type-2 trisaccharide (390 muM), an HBGA shown previously to be specifically recognized by human noroviruses. Importantly, competition STD NMR showed that citrate could compete with HBGA for norovirus binding. Together, the results suggest that citrate, and other glycomimetics, have the potential to block human noroviruses from binding to HBGAs.