title: Proteins from the prokaryotic nucleoid. Interaction of nucleic acids with the 15 kDa Escherichia coli histone-like protein H-NS.
abstract: The interaction between nucleic acids and Escherichia coli H-NS, an abundant 15 kDa histone-like protein, has been studied by affinity chromatography, nitrocellulose filtration and fluorescence spectroscopy. Intrinsic fluorescence studies showed that the single Trp residue of H-NS (position 108) has a restricted mobility and is located within an hydrophobic region inaccessible to both anionic and cationic quenchers. Binding of H-NS to nucleic acids, however, results in a change of the microenvironment of the Trp residue and fluorescence quenching; from the titration curves obtained with addition of increasing amounts of poly(dA)-poly(dT) and poly(dC)-poly(dG) it can be estimated that an H-NS dimer in 1.5 x SSC binds DNA with an apparent Ka approximately equal to 1.1 x 10(4) M-1.bp-1. H-NS binds to double-stranded DNA with a higher affinity than the more abundant histone-like protein NS(HU) and, unlike NS, prefers double-stranded to single-stranded DNA and DNA to RNA; both monovalent and divalent cations are required for optimal binding.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002846:Chromatography, Affinity; D004269:DNA, Bacterial / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D007700:Kinetics; D011067:Poly dA-dT / Q000378:metabolism; D011089:Polydeoxyribonucleotides / Q000378:metabolism; D012329:RNA, Bacterial / Q000378:metabolism; D014364:Tryptophan
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D011089:Polydeoxyribonucleotides; D012329:RNA, Bacterial; C040330:histone-like protein HU, bacteria; D011067:Poly dA-dT; C019530:poly(dC-dG); D014364:Tryptophan