Protein Expression in Yeast

Expression of proteins in yeast is a common alternative to prokaryotic and higher eukaryotic expression. Yeast cells offer many of the advantages of producing proteins in microbes (growth speed, easy genetic manipulation, low cost media) while offering some of the attributes of higher eukaryotic systems (post translational modifications, secretory expression). Several yeast protein expression systems exist in organisms from the genera Saccharomyces, Pichia, Kluyveromyces, Hansenula and Yarrowia.

At the heart of any yeast expression system is the expression vector. Vectors that integrate into the host chromosome are most widely used because of their mitotic stability in the absence of a selection. However, episomal expression vectors exist for some yeast systems. Expression vectors typically contain a strong yeast promoter/terminator and a yeast selectable marker cassette. Most yeast vectors can be propagated and amplified in E. coli to facilitate cloning and as such, also contain an E. coli replication origin and ampicillin selectable marker. Finally, many yeast expression vectors include the ability to optionally clone a gene downstream of an efficient secretion leader (usually that of mating factor) that efficiently directs a heterologous protein to become secreted from the cell.

A growing number of engineered yeast strains are becoming available for protein expression. Strains have been described that increase yield of secreted proteins, improve the performance of certain affinity tags, reduce proteolysis, define the composition of N-glycans, and permit non-native amino acids (e.g. selenomethionine) into proteins.

The system was adapted for life sciences research by NEB and a variety of vectors and host strains in a frozen competent format are offered.