Citron kinase essential for cytokinesis and neuronal progenitor cell division; mutations linked to microcephaly. Recombinant human STK21 (CIT) (1-449) was expressed by baculovirus in Sf9 insect cells using an N-terminal GST tag. Molecular weight ~74 kDa. Supplied as sterile 50 mM Tris-HCl, pH 7.5, 50-300mM NaCl, 10mM glutathione, 0.1mM EDTA, 0.25-1.0mM DTT, 0-0.1mM PMSF, 10-25% glycerol. Store product at –70°C. For optimal storage, aliquot target into smaller quantities. Avoid repeated handling and multiple freeze/thaw cycles.