Abstract
Dengue fever is a mosquito-borne endemic disease in tropical and subtropical regions, causing a significant public health problem in Southeast Asia. Domain III (ED3) of the viral envelope protein contains the two dominant putative epitopes and part of the heparin sulfate receptor binding region that drives the dengue virus (DENV)’s fusion with the host cell. Here, we used high-hydrostatic-pressure nuclear magnetic resonance (HHP-NMR) to obtain residue-specific information on the folding process of domain III from serotype 4 dengue virus (DEN4-ED3), which adopts the classical three-dimensional (3D) ß-sandwich structure known as the Ig-like fold. Interestingly, the folding pathway of DEN4-ED3 shares similarities with that of the Titin I27 module, which also adopts an Ig-like fold, but is functionally unrelated to ED3. For both proteins, the unfolding process starts by the disruption of the N- and C-terminal strands on one edge of the ß-sandwich, yielding a folding intermediate stable over a substantial pressure range (from 600 to 1000 bar). In contrast to this similarity, pressure-jump kinetics indicated that the folding transition state is considerably more hydrated in DEN4-ED3 than in Titin I27.
Highlights
Dengue fever, endemic in tropical and subtropical regions, is a significant public health problem in Southeast Asia [1], and no effective vaccine or specific medication is available [2]
The indolic proton HN resonances of the native and unfolded protein species were used to monitor DEN4-ED3 unfolding with pressure, using 1D nuclear magnetic resonance (NMR) spectroscopy (Figure 1): they are well individualized and do not overlap with HN amide resonances in the 1D spectrum of DEN4-ED3, and easy to follow
High-hydrostatic-pressure NMR was used to analyze at a residue-level resolution the folding pathway of DE4-ED3, an Ig-like protein domain from the dengue virus envelope
Summary
Endemic in tropical and subtropical regions, is a significant public health problem in Southeast Asia [1], and no effective vaccine or specific medication is available [2]. Over 33 million cases of dengue fever with several death cases are reported every year [3]. Dengue fever is caused by the mosquito-borne dengue virus (DENV), which is an enveloped, single-stranded, positive-sense. Infection by a single serotype provokes a mild to high fever for a few days, after which the patient usually recovers steadily and gains a long-lasting immunity against the infecting serotype. Subsequent heterotypic infections increase the risk of developing dengue haemorrhagic fever (DHF) and shock syndrome (DHS) with a ~5% mortality rate and severe complications [4,5]
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