CSK is a tyrosine-protein kinase CSK that plays an important role in the regulation of cell growth, differentiation, migration and immune response. Suppresses signaling by various surface receptors, including T-cell receptor (TCR) and B-cell receptor (BCR) by phosphorylating and maintaining inactive several positive effectors such as FYN or LCK.. Recombinant human CSK protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.