Production of selenomethionyl proteins in prokaryotic and eukaryotic expression systems

The use of selenomethionine as a phasing tool was first reported in 1990. Engineering of selenomethionyl proteins for structure determination is now routine. In fact, selenium is by far the most commonly used anomalous scatterer for multiwavelength anomalous diffraction studies. The past few years have seen new developments, which demonstrated the feasibility of expressing selenomethionyl protein in eukaryotic systems. In this chapter, the different methods available for producing selenomethionine-labeled proteins in bacteria, as well as in yeast and mammalian cells will be presented, along with tips for purifying and crystallizing selenomethionyl proteins.