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Expression of tetanus toxin fragment C
J Clare1, K Sreekrishna, M Romanos
1Medicines Research Centre, Glaxo-Wellcome, Stevenage, UK.
Methods in Molecular Biology (Clifton, N.J.)
|July 29, 1998
Summary
High gene copy number in P. pastoris fermentation significantly boosts protein fragment C yield. Controlled fermenters achieve 12 g/L, a 10-fold increase over shake-flasks, by optimizing cell density and induction efficiency.
Area of Science:
- Biotechnology
- Molecular Biology
- Protein Expression
Background:
- Optimizing recombinant protein production in microbial hosts is crucial for industrial applications.
- Pichia pastoris (P. pastoris) is a widely used yeast for high-level protein expression.
- Understanding factors influencing protein yield, such as gene copy number and fermentation conditions, is essential.
Purpose of the Study:
- To investigate the key factors affecting the yield of fragment C in P. pastoris.
- To compare protein yields achieved in shake-flask cultures versus controlled fermenters.
- To explore the relationship between gene dosage, integration events, and protein accumulation.
Main Methods:
- Utilized P. pastoris as a host for recombinant protein expression.
- Employed transplacement transformation to generate transformants with varying gene copy numbers.
- Conducted experiments in both shake-flasks and controlled fermenters.
- Analyzed protein accumulation by quantifying fragment C as a percentage of total protein.
Main Results:
- Fragment C accumulation strongly correlated with gene dosage, requiring high copy numbers for maximal expression.
- Controlled fermenter conditions significantly increased yields (2.5- to 10-fold) compared to shake-flasks due to high cell density and efficient induction.
- A 14-copy strain in fermenters achieved 27% fragment C of total protein, yielding 12 g/L.
- Observed significant clonal variation in expression levels attributed to diverse integration events and gene copy numbers.
Conclusions:
- High gene copy number and optimized fermentation conditions are critical for maximizing recombinant protein yields in P. pastoris.
- Multicopy transplacement events in P. pastoris likely involve in vivo circularization and single-crossover integration, a potentially generalizable phenomenon.
- Controlled fermenters offer a superior platform for achieving high-density cell cultures and efficient induction, leading to substantially higher protein yields.