Different efficiency of UmuDC and MucAB proteins in UV light induced mutagenesis in Escherichia coli

✍ Scribed by Blanco, Manuel ;Herrera, Guadalupe ;Aleixandre, Vicente

• Publisher: Springer
• Year: 1986
• Tongue: English
• Weight: 563 KB
• Volume: 205
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00430433

✦ Synopsis

Two multicopy plasmids carrying either the umuDC or the mueAB operon were used to compare the efficiency of UmuDC and MucAB proteins in UV mutagenesis of Eseheriehia coli K12. It was found that in recA + uvr + bacteria, plasmid pIC80, mucAB + mediated UV mutagenesis more efficiently than did plasmid pSE117, umuDC + . A similar result was obtained in lexA51(Def) cells, excluding the possibility that this was due to a differential regulation by LexA of the umuDC and mucAB operons. We conclude that some structural characteristic of the UmuDC and MucAB proteins determines their different efficiency in UV mutagenesis. This characteristic could be also responsible for the observation that in the reeA430 mutant, pIC80 but no pSE117 can mediate UV mutagenesis. In the reeA142 mutant, pIC80 also promoted UV mutagenesis more efficiently than pSEll7. In this mutant, the recombination proficiency, the protease activity toward LexA and the mutation frequency were increased by the presence of adenine in the medium. In recA + uvrB5 bacteria, plasmid pSEI 17, umuDC caused both an increase in UV sensitivity as well as a reduction in the mutation frequency. These negative effects resulting from the overproduction of UmuDC proteins were higher in reeA142 uvrB5 than in reeA + uvrB5 cells. In contrast, overproduction of MucAB proteins in excision-deficient bacteria containing pIC80 led to a large increase in the mutation frequency. We suggest that the functional differences between UmuDC and Mu-cAB proteins might be due to their different dependence on the direct role of RecA protease in UV mutagenesis.