Binding of DNA in vitro by a small, acid-soluble spore protein from Bacillus subtilis and the effect of this binding on DNA topology.
The DNA within spores of Bacillus subtilis is complexed with a large amount of alpha/beta-type small, acid-soluble spore protein (SASP). Measurement of the interaction of a purified alpha/beta-type SASP with DNA in vitro by a filter binding assay showed that the binding saturated at one molecule of SASP per approximately 5 bp. SASP-DNA binding did not require a divalent cation, was optimal at pH 6.7, and was unaffected by salt up to 400 mM. Binding of SASP to relaxed plasmid DNA in the presence of topoisomerase I resulted in the introduction of 18 (for plasmid pUC19) or 36 (for plasmid pUB110) negative supertwists, a superhelical density similar to that found in several plasmids isolated from spores. The SASP-dependent introduction of negative supertwists did not require a divalent cation, was unaffected by salt, and also gave a value of one molecule of SASP per approximately 5 bp at saturation. There was at least one slow step in the binding of SASP to DNA as seen in both the filter binding and supercoiling assays.
Nicholson
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WL
Department of Biochemistry, University of Connecticut Health Center, Farmington 06032.
Setlow
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Setlow
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D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism* / Q000648:ultrastructure; D004278:DNA, Superhelical / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D010957:Plasmids; D015183:Restriction Mapping; D013171:Spores, Bacterial
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D004492:Edetic Acid