Playing catch-up with Escherichia coli: using yeast to increase success rates in recombinant protein production experiments

Abstract

Several host systems are available for the production of recombinant proteins, ranging from Escherichia coli to mammalian cell-lines. This article highlights the benefits of using yeast, especially for more challenging targets such as membrane proteins. On account of the wide range of molecular, genetic, and microbiological tools available, use of the well-studied model organism, Saccharomyces cerevisiae, provides many opportunities to optimize the functional yields of a target protein. Despite this wealth of resources, it is surprisingly under-used. In contrast, Pichia pastoris, a relative new-comer as a host organism, is already becoming a popular choice, particularly because of the ease with which high biomass (and hence recombinant protein) yields can be achieved. In the last few years, advances have been made in understanding how a yeast cell responds to the stress of producing a recombinant protein and how this information can be used to identify improved host strains in order to increase functional yields. Given these advantages, and their industrial importance in the production of biopharmaceuticals, I argue that S. cerevisiae and P. pastoris should be considered at an early stage in any serious strategy to produce proteins.

Keywords: Pichia pastoris; Saccharomyces cerevisiae; choice of expression host; recombinant protein; yeast; yield optimization.

FIGURE 1

Strain selection enables the production of a human membrane protein in S. cerevisiae. Yeast cells were transformed with a plasmid expressing a construct encoding a human membrane protein tagged with green fluorescent protein. Expression was driven from a constitutive promoter and cells were imaged using confocal microscopy with an upright Leica TCS SP5 system. The sample was excited with a visible argon laser at 488 nm and imaged using a 63× oil objective. The panels show confocal images with bright-field and fluorescence for (A) wild-type cells and (B) a mutant S. cerevisiae strain selected from a global screen for high yielding strains (Bonander et al., 2005). Only the mutant cells produced correctly localized protein.