title: A cellular single-stranded DNA-dependent ATPase associated with simian virus 40 chromatin.
abstract: A single-stranded DNA-dependent ATPase from monkey kidney tissue culture cells (CV-1) has been found associated with SV40 chromatin. This ATPase activity is distinguishable from the ATPase activity of T-antigen by the following properties: the Km for ATP, elution from phosphocellulose, and stimulation of the ATPase activity by single-stranded DNA but not by double-stranded DNA. The ATPase has been isolated and characterized from the nuclei of uninfected cells. ATP hydrolysis is dependent on single-stranded DNA and a divalent cation. The km values for ATP and single-stranded DNA are 0.024 mM and 0.09 microgram/ml, respectively. The affinity of the ATPase for single-stranded DNA is sufficiently high that the enzyme co-sediments with single-stranded DNA in glycerol gradients. The binding of single-stranded DNA is independent of ATP and MgCl2; however, ATP hydrolysis increases the exchange of enzyme between different DNA molecules. Form I (superhelical) SV40 DNA is also a substrate for ATPase binding, but relaxed Form I, Form II (nicked circular), and double-stranded linear SV40 DNAs are not substrates. Because the DNA helix within chromatin is not under the same kind of tortional strain as Form I DNA, we hypothesize that the ATPase is bound to the single-stranded regions of replication forks in the SV40 chromatin.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D002522:Chlorocebus aethiops; D002843:Chromatin / Q000201:enzymology*; D007668:Kidney; D007700:Kinetics; D008970:Molecular Weight; D013539:Simian virus 40 / Q000201:enzymology*
chemical_list: D002843:Chromatin; D000251:Adenosine Triphosphatases; C037693:single stranded DNA dependent ATPase