title: Solubility enhancement of aggregation-prone heterologous proteins by fusion expression using stress-responsive Escherichia coli protein, RpoS.
abstract: BACKGROUND
  The most efficient method for enhancing solubility of recombinant proteins appears to use the fusion expression partners. Although commercial fusion partners including maltose binding protein and glutathione-S-transferase have shown good performance in enhancing the solubility, they cannot be used for the proprietory production of commercially value-added proteins and likely cannot serve as universal helpers to solve all protein solubility and folding issues. Thus, novel fusion partners will continue to be developed through systematic investigations including proteome mining presented in this study.
  
  
  RESULTS
  We analyzed the Escherichia coli proteome response to the exogenous stress of guanidine hydrochloride using 2-dimensional gel electrophoresis and found that RpoS (RNA polymerase sigma factor) was significantly stress responsive. While under the stress condition the total number of soluble proteins decreased by about 7 %, but a 6-fold increase in the level of RpoS was observed, indicating that RpoS is a stress-induced protein. As an N-terminus fusion expression partner, RpoS increased significantly the solubility of many aggregation-prone heterologous proteins in E. coli cytoplasm, indicating that RpoS is a very effective solubility enhancer for the synthesis of many recombinant proteins. RpoS was also well suited for the production of a biologically active fusion mutant of Pseudomonas putida cutinase.
  
  
  CONCLUSIONS
  RpoS is highly effective as a strong solubility enhancer for aggregation-prone heterologous proteins when it is used as a fusion expression partner in an E. coli expression system. The results of these findings may, therefore, be useful in the production of other biologically active industrial enzymes, as successfully demonstrated by cutinase.
authors.affiliation: Department of Chemical and Biological Engineering, Korea University, Anam-Dong 5-1, Sungbuk-Ku, Seoul 136-713, South Korea. anorain@korea.ac.kr
authors.forename: Jin-Seung
authors.initials: JS
authors.lastname: Park
authors.forename: Kyung-Yeon
authors.initials: KY
authors.lastname: Han
authors.forename: Jong-Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Jong-Am
authors.initials: JA
authors.lastname: Song
authors.forename: Keum-Young
authors.initials: KY
authors.lastname: Ahn
authors.forename: Hyuk-Seong
authors.initials: HS
authors.lastname: Seo
authors.forename: Sang-Jun Jun
authors.initials: SJ
authors.lastname: Sim
authors.forename: Seung-Wook
authors.initials: SW
authors.lastname: Kim
authors.forename: Jeewon
authors.initials: J
authors.lastname: Lee
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D011485:Protein Binding; D015202:Protein Engineering / Q000379:methods*; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D012995:Solubility
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011993:Recombinant Fusion Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria