Chardot T, Shen H, Meunier J C
Laboratoire de chimie biologique, INRA/INA/PG, Centre de biotechnologie agro-industrielle, Thiverval-Grignon, France.
C R Acad Sci III. 1995 Sep;318(9):937-42.
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 used 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.
在蛋白激酶的情况下，尤其是酪蛋白激酶II（CKII），已发现自身磷酸化的氨基酸类型与底物上的靶向氨基酸之间存在联系。在Mg2+存在的情况下，解脂耶氏酵母的CKII在丝氨酸和苏氨酸上发生自身磷酸化，并且当以酪蛋白作为底物时，主要发现丝氨酸苏氨酸激酶活性。在Mn2+存在的情况下，CKII在丝氨酸上的自身磷酸化受到抑制，而在酪氨酸上的自身磷酸化（在前一种情况下可忽略不计）变得显著。然后发现酪蛋白上会发生酪氨酸磷酸化。Mn2+将CKII转化为具有双重特异性的蛋白激酶，将其特异性从丝氨酸/苏氨酸激酶转变为丝氨酸/苏氨酸和酪氨酸激酶。Mn2+降低了观察到的丝氨酸和苏氨酸磷酸化水平，而另一方面促进了酪氨酸激酶活性。
