• The expression of recombinant proteins by self-inducible expression systems containing different human heat shock proteins in Ecoli
  • zahra sedighi,1 Fatemeh Sadat Shariati,2 Faezeh Takhsha,3 Zahra Parandeh,4 Arefe Sadat Khavari,5 Reza Ahangari Cohan,6,*
    1. department of Medical Biotechnology , Faculty of Medicine, Shahed University, Tehran , Iran
    2. Infulenza Research Lab , Pasteur Institute of Iran , Tehran , Iran
    3. Department of Stem Cells and Developmental Biology, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran
    4. Department of Biotechnology , school of Advanced Technologist in Medicine , Shahid Beheshti university of Medical Sciences , Tehran , Iran
    5. Department of Biology , College of Basic Sciences , Shahed university , Tehran , Iran
    6. Department of Nanobiotechnology , NewTechnologies Research Group , Pasteur Institute of Iran ,Tehran ,Iran


  • Introduction: The IPTG-inducible promoter is widely used for the expression of recombinant proteins. however, it is not suitable for industrial scale due to high cost and toxicity to the producing cells. Recently, a self-inducible expression (SILEX) system has been developed to overcome these problems by using Hsp70 as an autoinducer. here the effects of other heat shock proteins on the autoinduction of green fluorescent protein (EGFP) was investigated.
  • Methods: EGFP expression was monitored after double transformation of pET28a-EGFP and pET21a-(Hsp27/Hsp40/Hsp70) plasmids in E. coli using fluorimetry and SDS-PAGE. expression levels, bacterial growth curves, plasmid stability, and expression stability were compared with an IPTG-inducible system.
  • Results: Statistical analysis revealed a significant difference in EGFP expression between autoinducible and IPTG-inducible systems. Expression is higher in the Hsp27 than in the Hsp70 and Hsp40 systems. However The highest expression was observed in the inducible system. IPTG-inducible and Hsp70 systems showed longer lag times in the bacterial growth curve than Hsp27 and Hsp40 systems. In addition, Hsp27 and Hsp40 systems showed the same plasmid stability whitin 500 days of subculture, whereas Hsp70 showed a reduction in the numbers of colon in the first subculture step. Relatively stable EGFP expression was observed in the SILEX systems after several freeze-thaw cycles whitin 90 days, while the IPTG-inducible system showed a decreasing trend compared to the newly transformed bacteria . In addition, the inducible system showed more variation in experssion between different clones than the SILEX systems.
  • Conclusion: In conclusion, the Hsp27 system could be considered as a suitable autoinducible system for protein expression due to less metabolic burden, lower variation in expression, suitable plasmid and expression stability and higher expression level.
  • Keywords: Autoinducible expression system, Escherichia coli, SILEX system, Enhanced green fluorescent protein