Efficient expression and mutation of avidin and streptavidin as host proteins for enantioselective catalysis

Avidin and structurally related streptavidin are attractive host proteins for the creation of artificial metalloenzymes displaying features reminiscent both of homogeneous catalysts and enzymes. The main advantages are that both proteins have been cloned and expressed in several organisms and possess a deep hydrophobic binding pocket capable of hosting biotinylated catalyst precursors. An optimized artificial avidin gene in Pichia pastoris is expressed. The high level of active protein produced in the extracellular medium is suitable for the performance of high-throughput screening in 96-well plate format. Biologically active recombinant streptavidin is expressed in E. coli. Mutations have been introduced both in avidin and streptavidin genes and both wild type and mutated proteins have been utilized to explore the role of the second coordination sphere in enantioselective catalysis.