Bacterial expression, purification, and crystallization of tyrosine phosphorylated STAT proteins

Abstract

Signal Transducer and Activator of Transcription (STAT) proteins are latent cytoplasmic transcription factors that become activated by phosphorylation at a C-terminal tyrosine residue. Upon activation STAT proteins translocate to the nucleus and bind to their speci fic target sites. Here, we describe the recombinant expression of tyrosine phosphorylated STAT proteins in bacteria. This method allows the production of large amounts of activated STAT proteins for structural and biochemical studies including the highthroughput screening of chemical libraries.