Proteins from the prokaryotic nucleoid

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Abstract
The interaction of the prokaryotic DNA‐scaffolding proteins NS (from Escherichia coli and BS‐NS (from Bacillus stearothermophilus) with DNA has been investigated. Upon binding of NS to DNA, the resolution of its 400 MHz 1H‐NMR spectrum is lost, due to the broadening of all resonance lines. These effects are reversed by increasing the ionic strength. Since with increasing amounts of DNA added all resonances broaden progressively and simultaneously without prior selective loss of the spectral features due to the tertiary and quarternary structure of the protein, it is suggested that NS binds to DNA in the aggregated form (octameric?) and without gross alteration of its tertiary structure. By selective chemical modification of BS‐NS it was found that at least one Arg residue, located in the major hydrophilic, positively charged, conserved peptide of the protein (positions 51–70) is necessary for the interaction of BS‐NS with DNA.