engleski

Recombinational repair in the presence of lambda Gam protein in Escherichia coli

The RecBCD enzyme of Escherichia coli is involved in homologous recombination, DNA repair and degradation of foreign and damaged host DNA. Interaction of the RecBCD enzyme with λ Gam protein in vitro results in inhibition of all enzymatic activities of the RecBCD enzyme required for the formation of presynaptic filament. On the other hand, the presence of Gam protein in vivo abolishes only DNA degradation implying that RecBCD-Gam complex in vivo retains its helicase and RecA loading activities. To test whether RecBCD-Gam complex has RecA loading function in vivo, we studied the RecBCD-Gam mediated recombinational repair after γ and UV irradiation in wild type (wt), recO and recB1080 mutant which is deficient in nuclease and RecA loading function. We found that recombinational repair in wt cells is not dependent on recO mutation, and consequently concluded that RecBCD-Gam complex has its own RecA loading function in vivo. Contrary, the recombinational repair in recB1080 mutant is dependent on recO gene product which means that RecFOR system provides a RecA loading function for the RecB1080CD-Gam complex. We also found that RecB1080CD-Gam pathway of recombinational repair requires RecJ nuclease and partially RecQ helicase.

lambda; gam protein; RecBCD; E. coli

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