RESUMO
Plasmids pKS5 and pKSrec30 carrying normal and mutant alleles of Deinococcus radiodurans recA gene controlled by the lactose promoter slightly increase radioresistance of Escherichia coli cells with mutations at genes recA and ssb. The RecA protein of D. radiodurans is expressed in E. coli cells, and its synthesis can be supplementary induced. The radioprotective effect of the xenologic protein does not exceed 1.5 times and is essentially to the contribution of plasmid pUC 19-recA1.1 harboring the E. coli recA+ gene in the recovery of resistance of the deltarecA deletion mutant. These data suggest that the expression of D. radiodurans recA gene in E. coli cells does not complement mutations at gene recA in the chromosome possibly due to structural and functional peculiarities of the D. radiodurans RecA protein.
Assuntos
Proteínas de Bactérias/biossíntese , Deinococcus , Escherichia coli , Raios gama , Tolerância a Radiação/efeitos da radiação , Recombinases Rec A/biossíntese , Proteínas Recombinantes/biossíntese , Proteínas de Bactérias/genética , Tolerância a Radiação/genética , Recombinases Rec A/genética , Proteínas Recombinantes/genética , Especificidade da EspécieRESUMO
Bacterial RecA protein is the key enzyme in the processes of homologous recombination, post-replication repair and induction of SOS-repair functions. While a significant amount of data on the structure of RecA protein and its functional analogs has been obtained, there is little information about the molecular dynamics of this protein. In this work we present the results of neutron spin-echo measurements of the relaxation kinetics of filaments formed by RecA proteins from E. coli and P. aeruginosa. The results suggest that the protein filaments exhibit both diffusion and internal relaxation modes, which change during the formation of complexes of these proteins with ATP and single-stranded DNA.
Assuntos
Trifosfato de Adenosina/química , DNA de Cadeia Simples/química , Proteínas de Escherichia coli/química , Escherichia coli/enzimologia , Nêutrons , Pseudomonas aeruginosa/enzimologia , Recombinases Rec A/química , Trifosfato de Adenosina/metabolismo , Reparo do DNA/fisiologia , Replicação do DNA/fisiologia , DNA de Cadeia Simples/metabolismo , Proteínas de Escherichia coli/metabolismo , Estrutura Quaternária de Proteína , Recombinases Rec A/metabolismo , Recombinação Genética/fisiologia , Relação Estrutura-AtividadeRESUMO
The unicellular green microalga Chlamydomonas reinhardtii is a perspective model object for basic and applied research. However, its homologous recombination (HR) system which lies in the basis of double-strand DNA break repair have still not been studied. Last years the program of C. reinhardtii nuclear genome sequence is realized and different nucleotide repeats in the genome structure have been revealed that can explain a low level of HR relative to nonhomologous recombination events. Analyses of the C. reinhardtii EST (Expressed Sequence Tag)--and genome libraries permitted us to reconstruct and clone cDNA of the RAD51 gene. In present work, the cDNA was expressed, its product was purified and some basal biochemical activities were studied. The results show that Rad51C protein from lower eukaryote C. reinhardtii is identified as typical representative of the Rad51C-like subfamily of higher eukaryotes.
