DNA in dormant spores of Bacillus species is in an A-like conformation.
The DNA in dormant spores of Bacillus species is associated with alpha/beta-type small, acid-soluble proteins (SASP), which are double-stranded DNA-binding proteins whose amino acid sequence has been highly conserved in evolution. In vitro these proteins bind most strongly to DNA which readily adopts an A-like conformation, as binding of alpha/beta-type SASP causes DNA to assume an A-like conformation. As predicted by this conformational change in DNA, binding of alpha/beta-type SASP to relaxed but covalently closed plasmid DNA results in the introduction of a large number of negative supercoils. Associated with the conformational change in DNA brought about by alpha/beta-type SASP binding is a change in its photochemistry such that ultraviolet irradiation does not generate pyrimidine dimers, but rather a thyminyl-thymine adduct termed spore photoproduct (SP). The latter two properties of DNA complexed with alpha/beta-type SASP in vitro are similar to those of DNA in dormant spores of Bacillus species in which: (i) plasmid DNA has a much higher number of negative supercoils than plasmid in growing cells; and (ii) ultraviolet irradiation produces SP and no pyrimidine dimers, while only pyrimidine dimers are formed in growing cells. During sporulation these changes in the properties of spore DNA take place in parallel with synthesis of alpha/beta-type SASP, and the magnitude of the changes is greatly reduced in mutants that make low amounts of these proteins. A straightforward interpretation of these data is that DNA in dormant spores of Bacillus species is in an A-like conformation.(ABSTRACT TRUNCATED AT 250 WORDS)
Setlow
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Department of Biochemistry, University of Connecticut Health Center, Farmington 06030.
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics* / Q000502:physiology; D001426:Bacterial Proteins / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012808:Sigma Factor; D013171:Spores, Bacterial / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012808:Sigma Factor; D014157:Transcription Factors; C092468:spoIIR protein, Bacillus subtilis; C030069:spore-specific proteins, Bacillus