title: Non-chromatographic Method for the Hepatitis B Virus X Protein Using Elastin-Like Polypeptide Fusion Protein.
abstract: OBJECTIVE
  Hepatitis B virus (HBV) is a member of the hepadnavirus family. The HBV genome contains four genes designated as S, C, P, and X. The HBV X (HBx) gene encodes for a 16.5-kDa regulatory protein that enhances HBV replication and exerts multifunctional activities. The aim of this study is to describe the rapid and easy purification of HBx using ELP (elastin-like polypeptide) fusion protein.
  
  
  METHODS
  The ELP-HBx fusion protein was overexpressed in Escherichia coli. Environmental sensitivity was demonstrated via turbidity and dynamic light scattering as a function of temperature. HBx was purified as an ELP fusion protein. ELPs are biopolymers of the pentapeptide repeat Val-Pro-Gly-Xaa-Gly that undergo an inverse temperature phase transition. ELP follows in temperature and salt consistency, precipitation, and solution repetition (inverse transition cycling) with polypeptide, where it purifies the protein in a simple manner.
  
  
  RESULTS
  Fusion proteins underwent supramolecular aggregation at 40 ℃ in 1 M NaCl and slowly resolubilized at subphysiologic temperatures. ELP domain proteolysis liberated a peptide of comparable size and immunoreactivity to the commercial HBx.
  
  
  CONCLUSIONS
  This study suggests that HBx can be purified rapidly and easily using inverse transition cycling, and that this method can be applied in determination of HBx 3D structures and HBx stability study.
authors.affiliation: Division of High-Risk Pathogen Research, Korea National Institute of Health, Osong, Korea ; Department of Biochemistry, School of Medicine, Ajou University, Suwon, Korea.
authors.forename: Soon-Hwan
authors.initials: SH
authors.lastname: Kwon
authors.forename: Hyeseong
authors.initials: H
authors.lastname: Cho
keywords: HBx; elastin-like polypeptide; hepatitis B virus; inverse transition cycling; recombinant protein purification