title: Interaction of Escherichia coli host factor protein with Q beta ribonucleic acid.
abstract: The affinity of Escherichia coli host factor protein for a variety of ribonucleic acids (RNAs) is compared in an equilibrium competition assay with (pA)15 or (pA)27 as the common probe. Of the homopolymers tested, only polyriboadenylate [poly(rA)] binds the protein with a high affinity. At low ionic strength (0.1 M NaCl), the binding to Q beta RNA is much stronger than to the oligoadenylates, but the situation is reversed upon fragmentation of the RNA with ribonuclease T1. Increasing the ionic strength results in a drastic reduction of the affinity of host factor for Q beta RNA over a relatively narrow salt range (0.1--0.3 M NaCl). Over the same range, added salt greatly reduces the tendency of host factor hexamers to aggregate. The tight binding of host factor to Q beta RNA is proposed to result from the binding of an aggregate, which can interact with several low affinity sites on the RNA simultaneously.
mesh_terms: D001665:Binding Sites; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D002850:Chromatography, Gel; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D034982:Integration Host Factors; D009994:Osmolar Concentration; D011485:Protein Binding; D012329:RNA, Bacterial; D012367:RNA, Viral / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D034982:Integration Host Factors; C028696:Qbeta ribonucleic acid; D012329:RNA, Bacterial; D012367:RNA, Viral; C440502:integration host factor, E coli