Interaction of Escherichia Coli Host Factor Protein with Oligoriboadenylates

Pieter L. De Haseth, Olke C. Uhlenbeck

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


The interaction of Escherichia coli host factor 1 with oligoadenylate [oligo(A)] was studied by fluorescence and filter retention techniques. The intrinsic fluorescence of the host factor is quenched by up to 60% by the addition of oligo(A). Fluorescence titrations at high protein concentrations (6 μM) give a saturation point of 14 A residues per host factor hexamer regardless of chain length or ionic strength. Nitrocellulose filter retention experiments at much lower concentrations (1 nM) indicate equimolar complexes form between (pA), (12 < l < 27) and host factor hexamers. The smallest number of contiguous A residues which allows the formation of all favorable protein-RNA contacts is 16 at both low and high salt concentrations. At 0.1 M NaCl, the molar association constants are in the range of 10−10-1011 M−1 (15 < l < 27) and decrease only slightly with ionic strength, indicating a large nonionic component in the interaction. Cyclized (pA)l was shown to have a higher affinity for host factor than its linear counterparts when l is 18 or greater but a lower relative affinity when l is 15. This suggests that the binding site on the hexamer has a circular spatial orientation.

Original languageEnglish (US)
Pages (from-to)6138-6146
Number of pages9
Issue number26
StatePublished - Feb 1 1980

ASJC Scopus subject areas

  • Biochemistry


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