Hepatitis E virus capsid protein assembles in 4M urea in the presence of salts

Authors

  • Chunyan Yang,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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    • Chunyan Yang and Huirong Pan contributed equally to this work.

  • Huirong Pan,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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    • Chunyan Yang and Huirong Pan contributed equally to this work.

  • Minxi Wei,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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  • Xiao Zhang,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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  • Nan Wang,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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  • Ying Gu,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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  • Hailian Du,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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  • Jun Zhang,

    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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  • Shaowei Li,

    Corresponding author
    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
    • National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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  • Ningshao Xia

    Corresponding author
    1. National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
    • National Institute of Diagnostics and Vaccine Development in Infectious Disease, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China
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Abstract

The hepatitis E virus (HEV) capsid protein has been demonstrated to be able to assemble into particles in vitro. However, this process and the mechanism of protein–protein interactions during particle assembly remain unclear. In this study, we investigated the assembly mechanism of HEV structural protein subunits, the capsid protein p239 (aa368–606), using analytical ultracentrifugation. It was the first to observe that the p239 can form particles in 4M urea as a result of supplementation with salt, including ammonium sulfate [(NH4)2SO4], sodium sulfate (Na2SO4), sodium chloride (NaCl), and ammonium chloride (NH4Cl). Interestingly, it is the ionic strength that determines the efficiency of promoting particle assembly. The assembly rate was affected by temperature and salt concentration. When (NH4)2SO4 was used, assembling intermediates of p239 with sedimentation coefficient values of approximately 5 S, which were mostly dodecamers, were identified for the first time. A highly conserved 28-aa region (aa368–395) of p239 was found to be critical for particle assembly, and the hydrophobic residues Leu372, Leu375, and Leu395of p239 was found to be critical for particle assembly, which was revealed by site-directed mutagenesis. This study provides new insights into the assembly mechanism of native HEV, and contributes a valuable basis for further investigations of protein assembly by hydrophobic interactions under denaturing conditions.

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