Biotinylated proteins can be produced using Novagen's STP3-biotin kit. Commercial WGE systems are available from Ambion, Promega, and Roche Molecular Biologicals of Indianapolis. Since transcription and translation are coupled processes in bacteria, E. coli cell-free extracts are useful for coupled transcription and translation from DNA templates using either a phage or bacterial promoter. They are not generally suitable for translation of exogenous cellular RNA because these extracts contain endogenous nucleases. Because bacterial extracts do not require capped template RNAs, both prokaryotic and eukaryotic gene sequences can be efficiently translated in cell-free bacterial systems.
Bacterial extracts have a long pedigree.
These S30 bacterial extracts are still used today for in vitro translation studies 10 and to incorporate nonstandard amino acids into proteins for subsequent structural studies. Promega offers an E. coli T7 S30 Extract System for circular DNA templates that is ideal for translation of DNA sequences that contain a T7 promoter. The production of secondary products is significantly reduced with EcoPro when compared to traditional S30 extracts. Though in vitro translation systems typically produce small yields, Roche Molecular Biochemicals recently introduced the Rapid Translation System RTS 500 for preparative-scale protein expression. A single reaction can produce more than 500 g of product, and proteins greater than 120 kDa in size have been translated with this system.