Abstract
After the Bacillus subtilis nucleoid was dissected with restriction endonucleases, a specific DNA sequence from the purA region was isolated in a particulate form that probably originated from the cell membrane. Precise definition of the binding region within this sequence was achieved by a novel procedure based on a previously reported observation that additional copies of the binding region, introduced into the chromosome using an integrative plasmid, were also predominantly particle bound. Subsections of the original plasmid insertion were cloned into the integrative plasmid and introduced into B. subtilis, in which they became tandemly reiterated under appropriate selective conditions. HaeIII sites in the vector, flanking each insertion, were used to excise the latter for subsequent tests of particle association. Examination of 10 strains containing subsections of the original 5.2-kilobase-pair region showed that the binding region was confined to 283 base pairs. This was confirmed by dissection in vitro of a larger, isolated, particle-bound sequence. The nucleotide sequence of a 1,300-base-pair region that contained this site was determined. The entire region had a notably high A + T content and was deficient in open reading frames for transcription.