DUAL-SPECIFICITY OF CASEIN KINASE-II FROM THE YEAST YARROWIA-LIPOLYTICA

In the case of protein kinases, and especially in the case of casein kinase II (CKII), a link has been found between the type of the amino acids autophosphorylated and the targeted amino acids on the substrates. In the presence of Mg2+, CKII from the yeast Yarrowia lipolytica is autophosphorylated on serines and threonines, and a serine threonine Kinase activity is found predominantly when casein is wed as substrate. In the presence of Mn2+, CKII autophosphorylation is inhibited on serines, and autophosphorylation on tyrosines, negligible in the former case, becomes significant Tyrosine phosphorylation is then found to occur on casein. Mn2+ transforms CKII into a protein kinase with dual specificity, shifting its specificity from serine/threonine kinase towards a serine/threonine and tyrosine kinase. Mn2+ decreases the level of serine and threonine phosphorylation observed, while on the other hand promoting tyrosine kinase activity.