RESUMO
The transformation of Bacillus subtilis Lys- strains with plasmid pLRS33 containing pBR322 and the Bac. subtilis chromosomal fragment carrying the genes for lysin biosynthesis and the riboflavin operon regulatory operator region (ribO) leads to the appearance of Rib- mutants. It was shown that these mutants contained long deletions covering a great portion of the riboflavin operon.
Assuntos
Bacillus subtilis/genética , Cromossomos Bacterianos/ultraestrutura , Mutação , Plasmídeos , Riboflavina/genética , Bacillus subtilis/metabolismo , Bacillus subtilis/ultraestrutura , Deleção Cromossômica , Cromossomos Bacterianos/metabolismo , DNA Bacteriano/genética , Lisina/genética , Óperon , Recombinação Genética , Mapeamento por Restrição , Riboflavina/biossíntese , Transformação BacterianaRESUMO
Repression of synthesis of GTP-cyclohydrolase and riboflavinsynthetase was studied in different regulatory mutants of Bacillus subtilis. The results of experiments with some riboflavin precursors and their derivatives revealed that 5-amino-2,6-dioxo-4-ribitylaminopyrimidine and 6-methyl-7-(1',2'-dioxyethyl)-8-ribityllumazine can serve as effectors in riboflavin biosynthesis.
Assuntos
Bacillus subtilis/genética , Óperon , Riboflavina/biossíntese , Bacillus subtilis/enzimologia , Precursores Enzimáticos/metabolismo , Repressão Enzimática , GTP Cicloidrolase/análise , GTP Cicloidrolase/biossíntese , Genes Reguladores , Mutação , Pteridinas/metabolismo , Riboflavina/genética , Riboflavina Sintase/análise , Riboflavina Sintase/biossíntese , Espectrofotometria Ultravioleta , Uridina/análogos & derivados , Uridina/genética , Uridina/metabolismoRESUMO
Numerous operator-constitutive mutants of riboflavin biosynthesis were selected. All of them map in a short region of the Bacillus subtilis chromosome. The yield of riboflavin synthetase from this mutant is different, but in most cases much lower than the maximal yield from a repressor minus strain. Our tentative explanation is a partial overlap of the sites for the adsorption of repressor and RNA-polymerase. Therefore the affinity to the transcribing enzyme is diminished in the operator constitutive strains. The affinity of the repressor-effector complex to the operator depends on the effector structure.
Assuntos
Bacillus subtilis/genética , Genes Reguladores , Óperon , Riboflavina/genética , Mutação , Riboflavina Sintase/genética , Transformação BacterianaRESUMO
The incorporation of 14C-labelled guanosine and xanthosine into riboflavin was studied. It is concluded that the ribose mojety of guanosine is converted to the ribityl side chain of riboflavin. Thus the immediate precursor of riboflavin biosynthesis is a guanosine compound. Two classes of the riboflavin-dependent mutants of Bacillus subtilis were studied. They are closely linked to the lysine markers and probably correspond to the initial steps of riboflavin biosynthesis pathway.
