Effect of protein kinase ck2 on topoisomerase I from plasmodia of the slime mold Physarum polycephalum.

Relaxing activity of Physarum topoisomerase I was increased by calf thymus protein kinase ck2, similarly as was the activity of mammalian topoisomerase I, despite a pronounced difference between amino-acid sequences of non-conserved domains of Physarum and mammalian enzymes. This feature of Physarum topoisomerase I was cancelled in nuclear extracts isolated from dibutyryl-cAMP treated plasmodia in which the activity of protein kinase ck2 was elevated.