title: Expression and purification of the complete PreS region of hepatitis B Virus.
abstract: OBJECTIVE
  To express the complete PreS region of HBV in E.coli with good solubility and stability, and to establish an effective method for purification of the recombinant PreS protein.
  
  
  METHODS
  The complete PreS region (PreS1 and PreS2) was fused into a series of tags including glutathione S-transferase (GST), dihydrofolate reductase (DHFR), maltose binding protein (MBP), 6x histidine, chitin binding domain (CBD), and thioredoxin, respectively. Expression of recombinant PreS fusion proteins was examined by SDS-PAGE analysis and confirmed by Western blot. Two fusion proteins, thio-PreS, and PreS-CBD, with desirable solubility and stability, were subjected to affinity purification and further characterization.
  
  
  RESULTS
  Recombinant PreS fusion proteins could be synthesized with good yields in E.coli. However, most of these proteins except for thio-PreS and PreS-CBD were vulnerable to degradation or insoluble as revealed by SDS-PAGE and Western blot. Thio-PreS could be purified by affinity chromatography with nickel-chelating sepharose as the matrix. However, some impurities were also co-purified. A simple freeze-thaw treatment yielded most of the thio-PreS proteins in solution while the impurities were in the precipitate. Purified thio-PreS protein was capable of inhibiting the binding of HBV virion to a specific monoclonal antibody against an epitope within the PreS1 domain.
  
  
  CONCLUSIONS
  Increased solubility and stability of the complete PreS region synthesized in E.coli can be achieved by fusion with the thioredoxin or the CBD tag. A simple yet highly effective method has been established for the purification of the thio-PreS protein. Purified thio-PreS protein likely assumes a native conformation, which makes it an ideal candidate for studying the structure of the PreS region as well as for screening antivirals.
authors.affiliation: State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Deng
authors.forename: Yu-Ying
authors.initials: YY
authors.lastname: Kong
authors.forename: You-Hua
authors.initials: YH
authors.lastname: Xie
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D004926:Escherichia coli / Q000378:metabolism; D006514:Hepatitis B Surface Antigens / Q000096:biosynthesis* / Q000302:isolation & purification*; D006515:Hepatitis B virus / Q000502:physiology*; D011498:Protein Precursors / Q000096:biosynthesis* / Q000302:isolation & purification*; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000302:isolation & purification*; D014759:Viral Envelope Proteins / Q000096:biosynthesis* / Q000302:isolation & purification*
chemical_list: D006514:Hepatitis B Surface Antigens; D011498:Protein Precursors; D011994:Recombinant Proteins; D014759:Viral Envelope Proteins; C050806:presurface protein 1, hepatitis B surface antigen