Phospho-amino acid analysis of BbKst-kinase by thin-layer chromatography. 32P-labeled protein, after in vitro kinase reaction, was acid hydrolyzed. Hydrolyzed labelled amino acids were spotted along with three authentic markers of pSer, pThr, and pTyr amino acids on cellulose thin-layer chromatography plates and separated at high voltage. Marker phosphoamino acids were detected by ninhydrin staining; whereas, labeled phosphoamino acids were detected by autoradiography. UP represents unhydrolyzed protein.