Structural and functional characterization of the recR gene of Streptomyces
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O R I GI N A L P A P E R
A. I. PelaÂez á R. M. Ribas-Aparicio á A. GoÂmez M. R. Rodicio
Structural and functional characterization of the recR gene of Streptomyces Received: 26 October 2000 / Accepted: 8 January 2001 / Published online: 14 March 2001 Ó Springer-Verlag 2001
Abstract The recR gene product is necessary for homologous recombination and recombinational DNA repair in eubacteria. We report the isolation and sequencing of the recR gene from Streptomyces coelicolor. It encodes a protein of 198 amino acids, with a predicted molecular mass of 22 kDa. The deduced amino acid sequence shows signi®cant similarity to that of RecR proteins from other bacteria, including Escherichia coli and Bacillus subtilis. Like these, Streptomyces RecR contains potential helix-hairpin-helix, zinc ®nger and ATP-binding motifs, as well as the Toprim domain which is present also in topoisomerases of Types IA and II, primases and nucleases of the OLD family. The recR genes of Escherichia coli and Bacillus subtilis are immediately preceded by a small ORF (orf12 and orf107, respectively). An equivalent ORF (orf1) is also found in Streptomyces. S. lividans recR mutants, obtained either by insertional inactivation of recR or by deletion of the gene together with the preceding ORF, displayed increased sensitivity to DNA-damaging agents (such as UV light and methylmethanesulfonate), when compared with the wild-type strain. Both mutants could be complemented by the wild-type orf1recR genes and also by the recR gene alone. Based on these results, orf1 appears to be dispensable for the repair function of Streptomyces RecR. In studies of heterologous complementation, the B. subtilis recR region (orf107recR) was found to complement the S. lividans Dorf1recR mutant, but the Communicated by R. Devoret A. I. PelaÂez á A. GoÂmez á M. R. Rodicio (&) Departamento de BiologõÂ a Funcional (Area de MicrobiologõÂ a), Instituto Universitario de BiotecnologõÂ a (IUBA), Universidad de Oviedo, 33006 Oviedo, Spain E-mail: [email protected] Tel.: 34-985-103652 Fax: +34-985-103148 R. M. Ribas-Aparicio Departamento de MicrobiologõÂ a, Escuela Nacional de Ciencias BioloÂgicas del Instituto PoliteÂcnico Nacional, Mexico City DF, Mexico
equivalent region from E. coli (orf12recR) could not. However, in the absence of orf107, B. subtilis recR was unable to restore the wild-type phenotype to the Streptomyces deletion mutant. Keywords Streptomyces coelicolor á Streptomyces lividans á recR á Recombinational DNA repair á Genetic complementation
Introduction In Escherichia coli the RecF, RecO, and RecR proteins function together with RecA at an early stage in general recombination and in recombinational DNA repair of daughter-strand gaps by the RecF pathway (Kuzminov 1999; Cox 2000; Cox et al. 2000). Acting in pairs, they have an important role in modulating the assembly and disassembly of RecA ®laments. Thus, RecR together with RecO helps RecA to overcome the inhibitory eect of SSB (ssDNA-binding protein) during homologous pairing of ssDNA with dsDN
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