Yeast display

Yeast display (or yeast surface display) is a protein engineering technique that uses the expression of recombinant proteins incorporated into the cell wall of yeast for isolating and engineering antibodies.
Development.
The yeast display technique was first published by the laboratory of Professor K. Dane Wittrup. The technology was sold to Abbott Laboratories in 2001.
How it works.
A protein of interest is displayed as a fusion to the Aga2p protein on the surface of yeast. The Aga2p protein is naturally used by yeast to mediate cell–cell contacts during yeast cell mating. As such, display of a protein via Aga2p projects the protein away from the cell surface, minimizing potential interactions with other molecules on the yeast cell wall. The use of magnetic separation and flow cytometry in conjunction with a yeast display library is a highly effective method to isolate high affinity protein ligands against nearly any receptor through directed evolution.
Advantages and disadvantages.
Advantages of yeast display over other "in vitro" evolution methods include eukaryotic expression and processing, quality control mechanisms of the eukaryotic secretory pathway, minimal avidity effects, and quantitative library screening through fluorescent-activated cell sorting (FACS). Yeast are eukaryotic organisms that allow for complex post-translational modifications to proteins that no other display libraries are able to provide.
Disadvantages include smaller mutant library sizes compared to alternative methods and differential glycosylation in yeast compared to mammalian cells. These disadvantages have not limited the success of yeast display for a number of applications, including engineering the highest monovalent ligand-binding affinity reported to date for an engineered protein (Boder, E.T. 2000). Currently the yeast display library created by Boder is no longer available, as the INVSc1 cell line from Invitrogen is no longer available due to IP issues.
Alternative methods for protein evolution "in vitro" are mammalian display, phage display, ribosome display, bacterial display, and mRNA display.