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Abstract
We have determined the changes in DNA sequence corresponding to three mutations in the promoter-proximal open reading frame of spoIIA, a locus that regulates sporulation in Bacillus subtilis. All three mutations prevent the synthesis of two sporulation-associated enzymes, but they differ in their effects on spore incidence. We now find that mutation spo-42, which allows spores to be produced at a low incidence, is a transition that changes Gly95 to Asp in the protein encoded by the open reading frame. Mutation spo-69, which blocks sporulation entirely, consists of two transitions: these change Gly62 to Asp and Ala116 to Thr. Mutation sas-1, which partially suppresses spo-69, is also a transition : this changes residue 62 (which had become Asp as a result of the spo-69 mutation) to Asn.
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