Effect of the Strandedness of Cofactor DNA on the Activities of DNA-Dependent ATPases B and C3 from FM3A Cells

The requirements of cofactor DNA for DNA-dependent ATPases B and C3 were analyzed in detail. ATPase B and C3 required the pre-sence of a polynucleotide for their activities. Among the DNAs tested, ATP-ase B showed a preference for poly(dT) as its cofactor. The other deoxyhomo-polymers, except poly(dG) and heat-denatured DNA also were effective. The alternating polydeoxyribonucleotide, poly[d(A-T) ] had an efficiency 23 that of heat-denatured DNA. Unlike ATPase B, ATPase C3 showed almost no activity with deoxyhomopolymers. The most effective cofactor for ATPase C3 so far tested is poly[d(A-T) ]. Relatively high activity was obtained with heat-denatured DNA. The high activity of ATPase B with poly(dT) was reduc-ed by the addition of poly(dA). The addition of noncomplementary homo-polymers did not affect enzyme activity. ATPase C3 activity in the presence of 10 μM poly(dT) increased gradually with concentrations of poly(dA) up to 20 μM, after which it decreased. Almost no increase in activity was observed when noncomplementary homopolymers were added. The relatively high activ- ity of ATPase C3 with heat-denatured DNA was suggested by its high sensitivity to ethidium bromide to be due to the double-stranded region in the heat-denatured DNA formed by self-annealing.