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sbmC , a stationary‐phase induced SOS Escherichia coli gene, whose product protects cells from the DNA replication inhibitor microcin B17
Author(s) -
Baquero M.R.,
Bouzon M.,
Varea J.,
Moreno F.
Publication year - 1995
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1995.mmi_18020301.x
Subject(s) - biology , repressor lexa , escherichia coli , gene , regulon , dna replication , dna gyrase , dna , gene product , sos response , microbiology and biotechnology , transversion , genetics , biochemistry , gene expression , mutation , repressor
Microcin B17 (MccB17) is a ribosomally synthesized peptide antibiotic of 43 amino acids that induces double‐strand breaking of DNA in a DNA gyrase‐dependent reaction. As a consequence, the SOS regulon is induced and massive DNA degradation occurs. In this work we have characterized an Escherichia coli gene, sbmC , that in high copy number determines high cell resistance to MccB17. sbmC encodes a cytoplasmic polypeptide of 157 amino acids ( M r , 18 095) that has been visualized in SDS—polyacrylamide gels. The gene is located at min 44 of the E. coli genetic map, close to the sbcB gene. sbmC expression is induced by DNA‐damaging agents and, also, by the entry of cells into the stationary growth phase. A G → T transversion at the fifth nucleotide of the quasicanonical LexA‐box preceding the gene makes recA cells 16‐fold more resistant to exogenous MccB17. The gene product, SbmC, also blocks MccB17 export from producing cells. Altogether, our results suggest that SbmC recognizes and sequesters MccB17 in a reversible way.