Protein expression systems for structural genomics and proteomics

One of the key steps of structural genomics and proteomics is high-throughput expression of many target proteins. Gene cloning, especially by ligation-independent cloning techniques, and recombinant protein expression using microbial hosts such as Escherichia coli and the yeast Pichia pastoris are well optimized and further robotized. Cell-free protein synthesis systems have been developed for large-scale production of protein samples for NMR (stable-isotope labeling) and X-ray crystallography (selenomethionine substitution). Protein folding is still a major bottleneck in protein expression. Cell-based and cell-free methods for screening of suitable samples for structure determination have been developed for achieving a high success rate.