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Protein Expression System

Introduction

Protein expression systems are essential tools in biotechnology and life sciences, enabling the synthesis of recombinant proteins for use in therapeutics, diagnostics, and research. These systems utilize host organisms such as bacteria, mammalian cells, or insect cells to produce proteins with desired characteristics.

Common Protein Expression Systems

  • E. coli Expression System:

    E. coli is a widely used bacterial host for recombinant protein production, offering simplicity and cost-effectiveness.

    • Mechanisms: Recombinant genes are introduced via plasmid vectors with inducible promoters. Expression is induced with agents like IPTG, and proteins are extracted through cell lysis.
    • Challenges: E. coli often fails to process post-translational modifications (PTMs), limiting its application for complex eukaryotic proteins.
    • Applications: It is used in enzyme engineering, diagnostic antigens, and producing biopharmaceuticals like insulin.
  • CHO Cell Expression System:

    CHO cells are mammalian systems renowned for their ability to perform human-like PTMs, particularly glycosylation, crucial for therapeutic proteins.

    • Mechanisms: Genes encoding target proteins are transfected into CHO cells, leading to production, folding, and glycosylation before secretion.
    • Advantages: CHO systems are essential for manufacturing monoclonal antibodies (e.g., Trastuzumab) and other complex therapeutics.
  • Baculovirus/Insect Cell Expression System:

    The Baculovirus/Insect Cell System is a versatile eukaryotic expression platform leveraging the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) to infect insect cells, such as Spodoptera frugiperda (Sf9 or Sf21) or Trichoplusia ni (Hi-5).

    • Mechanisms:
      • Recombinant Baculovirus Production: Genes of interest are cloned into a baculovirus transfer vector under the control of a strong promoter (e.g., polyhedrin or p10 promoter).
      • Infection of Insect Cells: Recombinant baculoviruses infect insect cells, driving robust transcription and translation of the gene of interest.
      • Protein Processing: Insect cells perform eukaryotic PTMs, including glycosylation, phosphorylation, and disulfide bond formation, though glycoforms differ from mammalian cells.
      • Secretion or Intracellular Expression: Proteins are either secreted into the culture medium or retained intracellularly for purification.
    • Applications: Production of complex proteins, including viral antigens for vaccines (e.g., HPV vaccine Gardasil).

Challenges and Optimization Strategies

  • Post-Translational Modifications: Systems like E. coli lack machinery for PTMs; Baculovirus systems provide some PTMs, but the glycoforms are not identical to those produced in mammalian cells.
  • Aggregation: Protein aggregation in bacterial systems often necessitates refolding, while insect cells reduce this issue.
  • Yield and Cost: Mammalian systems like CHO are cost-intensive, whereas bacterial and insect systems balance cost and complexity.

GenScript's Role in Protein Expression

  • CHO Cells: TurboCHO™ platforms for high-yield therapeutic protein production.
  • E. coli Systems: Codon optimization and advanced purification services for bacterial hosts.
  • Insect Systems: Custom baculovirus production services, ensuring high-titer virus stocks and robust expression in insect cells.

Conclusion

Protein expression systems form the backbone of modern molecular biology and biopharmaceutical production. While bacterial systems like E. coli provide rapid, cost-effective solutions, mammalian systems such as CHO cells are essential for producing complex proteins with human-like modifications. The Baculovirus/Insect Cell Expression System complements bacterial and mammalian platforms by providing a balance between PTM capability and cost-efficiency. Continuous optimization of these systems for efficiency and specificity remains a critical area of innovation in biotechnology and life sciences.


Related Biology Tools

  • GenSmart™ Codon Optimization

    GenSmart Optimization is a free online tool for performing codon optimization to improve gene expression. GenScript's patented algorithms are integrated into the tool to optimize the computing capability of high-performance sequence generation.

    Learn More

  • DNA Construct Design Tool

    GenSmart™ Design is a free online DNA construct design tool developed by GenScript. GenSmart™ Design has two design modules, the Create Construct module for individual plasmid design and the Create Library module for DNA library design.

    Learn More

  • Codon Frequency Tables

    This online tool shows commonly used genetic codon frequency table in expression host organisms including Escherichia coli and other common host organisms.

    Learn More

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