FIG 5.
Analysis of assembly of sp239 protein from genotype 4 swine HEV to form polymers. (A) Monomers and dimers of sp239 with or without prior heat treatment in PB buffer were observed using modified SDS-PAGE. Lane M, molecular size markers; lane H, heated samples under reducing conditions (samples were heated to 100°C for 3 min with BME); lane N, unheated samples under nonreducing conditions (0.1% SDS in the absence of BME). (B) Size exclusion chromatography of sp239 purified using a Superdex 200 Increase 10/300 GL column. The inset shows the calibration of the column and the equation used for calculating the size of the sp239 complex. MW, molecular weight. Accordingly, Mr 632,000 polymeric and Mr 136,000 pentameric forms of sp239 were detected in peak I and peak II, respectively, during gel filtration using an ÄKTA purifier (GE Healthcare). (C) Bacterially expressed sp239 protein particles in PB7.5 were visualized using electron microscopy and exhibited diameters of approximately 23 nm.