A novel protein expression system-PichiaPink™- and a protocol for fast and efficient recombinant protein expression

Abstract

Pichia pastoris is a eukaryote and has many of the advantages of higher eukaryotic expression systems, such as protein processing, protein folding, and the availability of posttranslational modifications. It is as easy to manipulate as Escherichia coli or Saccharomyces cerevisiae. However, some serious and unavoidable problems occur with the Pichia pastoris system that is difficult to overcome, such as low transforming efficiency and degradation of protein. Recently, a new protein expression system named PichiaPink™ was introduced. We have used the pichia-based system to express some proteins successfully, such as human serum albumin, Ganoderma lucidum immunoregulatory protein (Lz-8), and found that the system can improve the transformation of the Pichia stain, the low yields and the degradation of the protein of interest. In the example of human serum albumin (HSA), the results indicated two facts: (1) the protease knockout PichiaPink™ strains are quite helpful in decreasing the degradation of HSA without affecting the yield of HSA or the strain growth, and the high-copy expression vector worked better than the low-copy expression vector in terms of the HSA yield. The example of rLz-8 showed that compared with the traditional Pichia strain Gs115, the new system provided an easier selection method for screening correct and higher level of expression transformants.

Key words: Pichia pastoris, protease knockout strain, ADE