A novel DNA helicase from calf thymus.

摘要: Abstract We report the purification and characterization of a novel DNA helicase from calf thymus tissue. This enzyme partially copurifies with polymerase epsilon* through many chromatographic procedures used to isolate it. The contains an intrinsic DNA-dependent ATPase activity. It can displace short oligonucleotides annealed long single stranded substrates, in ATP-dependent reaction. Use this assay indicates that translocates 3' 5' direction respect substrate strand which it is bound. Maximal efficiency displacement accomplished by hydrolysis (d)ATP as cofactor, however, (d)CTP also be utilized resulting 5-fold decrease level displacement. Displacement activity enhanced presence saturating amounts Escherichia coli DNA-binding protein, not affected phage T4 gene 32 inhibited human replication factor A. has molecular mass approximately 104 kDa measured denaturing gel electrophoresis, S value 5.4 obtained glycerol gradient sedimentation. Direct [alpha-32P]ATP cross-linking labels protein 105 kDa, providing further evidence polypeptide active site. In view differences properties four others recently identified designated A D, we propose name E.