Often the greatest challenge in initiating a drug discovery campaign against an unprecedented target is producing well-behaved, biologically relevant samples. Our protein sciences group is built around solving this problem with an abundance of experience and technologies at their fingertips.
We begin with a bioinformatics approach to generate a variety of constructs designed to encompass functional portions of the target. These are then screened for expression of soluble protein at small scale under a variety of conditions. Promising constructs are taken forward to scale up. Since the difference between a highly expressed soluble protein and an inclusion body depends on many different factors, we have developed our own proprietary vectors and tags for purification, immobilization and solubilization. We have also developed proprietary media for bacterial culture that enhances expression levels under a variety of conditions, including stable isotope labeling required for protein observed NMR studies. Where bacterial expression is not the best approach, we have ready access to expression in human cells.
Frequently finding the right construct and expression conditions is only half the battle though. The tendency of a protein to aggregate and/or precipitate is also strongly influenced by solution conditions. We have therefore developed our owns screens and readouts to assay thousands of combinations of reagents designed to improve the solubility and monodispersity of a protein sample while retaining or even enhancing biological activity. These optimized conditions are then utilized throughout our protein handling process to improve yields, increase the chances of obtaining highly diffracting crystals and improve the quality of data from biophysics studies.
While we all agree that highly-pure and active proteins are a prerequisite for target based studies, ZoBio goes further. We understand that proteins only function well when monodisperse, i.e. a homogenous solution of defined oligomeric state. We quantify these characteristics and define minimal criteria for accepting a protein preparation. For ZoBio, this means high purity, high monodispersity and highly active in an appropriate biochemical assay.