Purification and characterization of the coliphage N4-coded single-stranded DNA binding protein.

摘要: Abstract We have purified and characterized a single-stranded DNA binding protein (N4 SSB) induced after coliphage N4 infection. It has monomeric molecular weight of 31,000 contains 10 tyrosine 1-2 tryptophan amino acid residues. Its fluorescence spectrum is dominated by the residues, their quenched when binds DNA. Fluorescence quenching was used as an assay to quantitate nucleotides. The cooperatively nucleic acids more tightly than RNA. involves displacement cations from anions protein. apparent affinity very salt-dependent, decreasing much 1,000-fold for 10-fold increase in NaCl concentration. degree cooperativity (omega) relatively independent salt At 37 degrees C 0.22 M NaCl, intrinsic constant M13 viral 3.8 x 10(4) M-1, factor omega 300, site size 11 nucleotides per monomer. lowers melting point poly(dA.dT).poly(dA-dT) greater 60 but cannot lower transition or assist renaturation natural enhances rate synthesis catalyzed polymerase increasing processivity out hairpin structures that block polymerization.