Project

• What's the idea behind this expression system?
      Laboratory and industrial projects that involve the high volume production of a protein often select E. coli as an expression system due to its rapid growth. However, bacterial expression systems are not always a viable option. In the case where proper folding of the protein of interest requires post-translational modification (such as the addition of disulfide bonds or glycosylation,) a eukaryote must be used. Although several well-defined eukaryotic options exist, yeast is often selected for its ease of use in the laboratory. One yeast species in particular, Pichia pastoris, has gained popularity as an expression system for recombinant human proteins.

• Why did we choose P. Pastoris?
      P. pastoris has a glycosylation pattern that is more compatible with the human immune system, when compared to the glycosylation pattern of Saccharomyces cerevisiae. P. pastoris is also known for its ability to grow in high densities using methanol as its only food source. Despite the usefulness of yeast species such as P. pastoris there are currently few items in the parts registry that are designed for use within yeast, and none that are specifically designed to be used with P. pastoris. Our team intends on producing pBB3G1 and pBB1Z1, two BioBrick compatible P. pastoris-E. coli shuttle vectors.

• What are some benefits of this vector system?
      The pBB3G1 and pBB1Z1 vectors include features that increase its ease-of-use and versatility, such as: optional inducibility, optional product secretion, trans-kingdom conjugation (TKC), and episomal maintenance of the vector in the host organism. The vectors vary in their expression level. Constitutive expression is achieved in pBB1Z1 by the pGAP promoter. Methanol-induced expression is available in pBB3G1 by means of the pAOX1 promoter.

• Why use Trans Kingdom Conjugation instead of traditional transformation methods?
      TKC involves the transfer of DNA from a bacterial cell to a eukaryotic cell, by means of conjugation. Harnessing the ability to shuttle plasmids between E. coli and P. pastoris through TKC would simplify transformation protocols. Currently, transformation methods (using shuttle plasmids cloned in E. coli) are a time consuming process, requiring isolation of the cloned plasmid and transformation into yeast. Transformation using TKC shortens the process by transferring the plasmid directly into the yeast cell. Utilizing TKC as a transformation protocol would translate to faster results in the laboratory and reduced costs in an industrial setting. Currently there are no BioBrick vectors in the parts registry that enable TKC between E. coli and P. pastoris.

• How will TKC be achieved?