title: Loss of catabolite repression function of HPr, the phosphocarrier protein of the bacterial phosphotransferase system, affects expression of the cry4A toxin gene in Bacillus thuringiensis subsp. israelensis.
abstract: HPr, the phosphocarrier protein of the bacterial phosphotransferase system, mediates catabolite repression of a number of operons in gram-positive bacteria. In order to participate in the regulatory process, HPr is activated by phosphorylation of a conserved serine-46 residue. To study the potential role of HPr in the regulation of Cry4A protoxin synthesis in Bacillus thuringiensis subsp. israelensis, we produced a catabolite repression-negative mutant by replacing the wild-type copy of the ptsH gene with a mutated copy in which the conserved serine residue of HPr was replaced with an alanine. HPr isolated from the mutant strain was not phosphorylated at Ser-45 by HPr kinase, but phosphorylation at His-14 was found to occur normally. The enzyme I and HPr kinase activities of the mutant were not affected. Analysis of the B. thuringiensis subsp. israelensis mutant harboring ptsH-S45A in the chromosome showed that cry4A expression was derepressed from the inhibitory effect of glucose. The mutant strain produced both cry4A and sigma(35) gene transcripts 4 h ahead of the parent strain, but there was no effect on sigma(28) synthesis. In wild-type B. thuringiensis subsp. israelensis cells, cry4A mRNA was observed from 12 h onwards, while in the mutant it appeared at 8 h and was produced for a longer period. The total amount of cry4A transcripts produced by the mutant was higher than by the parent strain. There was a 60 to 70% reduction in the sporulation efficiency of the mutant B. thuringiensis subsp. israelensis strain compared to the wild-type strain.
authors.affiliation: Centre For Biotechnology, Jawaharlal Nehru University. International Centre For Genetic Engineering and Biotechnology, New Delhi, India.
authors.forename: Sharik R
authors.initials: SR
authors.lastname: Khan
authors.forename: Nirupama
authors.initials: N
authors.lastname: Banerjee-Bhatnagar
mesh_terms: D001413:Bacillus thuringiensis / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins; D004731:Endotoxins / Q000235:genetics / Q000378:metabolism*; D004794:Enzyme Repression; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D006460:Hemolysin Proteins; D007700:Kinetics; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D013171:Spores, Bacterial / Q000502:physiology; D014158:Transcription, Genetic
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004731:Endotoxins; C064971:FliA protein, Bacteria; D006460:Hemolysin Proteins; D012808:Sigma Factor; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D010770:Phosphotransferases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr; D005947:Glucose