Calcium is a cofactor of polymerization but inhibits pyrophosphorolysis by the Sulfolobus solfataricus DNA polymerase Dpo4.
Irimia A, Zang H, Loukachevitch LV, Eoff RL, Guengerich FP, Egli M. Calcium is a cofactor of polymerization but inhibits pyrophosphorolysis by the Sulfolobus solfataricus DNA polymerase Dpo4. Biochemistry. 2006 May 16; 45(19):5949-56.