3.1.21.3	phosphoprotein	HsdR subunit of isoform EcoKI is phosphorylated on Thr. Phosphorylation in vitro is strictly dependent on the addition of a catalytic amount of cytoplasmic fraction isolated from Escherichia coli. Phosphorylation in vivo only occurs when subunit HsdR is coproduced with subunits HsdM and HsdS	679909