RecA protein E. coli

Craig, N.L. Roberts, J.W. (1980). E. coli recA protein-directed cleavage of phage lambda requires polynucleotide. Nature (London) 283, 26-30. 

DNA-strand exchange between a ssDNA and a duplex in which all G and C residues have been replaced by 2 -deoxyisoguanosine (iG) and 2 -deoxy-5-methyl-isocytidine MiC) by the E. coli RecA protein in vitro occurred at a similar rate and efficiency to unmodified DNA. This provides further potential for the role of iG and MiC in an expanded genetic code. Using ODNs rich in isoguanosine residues, Chaput and Switzer have shown that iG quintet structures may be formed from a metal-assisted hydrogen bond-mediated self-assembly process. The structures were stabilised particularly in the presence of Cs+ ions. 

Tfe-REC is quite small (24,543 Da, p/ 9.69) compared to its bacterial and eukaryotic counterparts, with the N- and C-terminal regions being obviously truncated (Fig. lb). The crystal structure of E. coli RecA protein-ADP complex revealed a major domain that bound to ATP and single- and double-stranded DNAs, and two smaller subdomains at the N and C termini protruded from the major domain. Deletion analysis of the N-terminal 33 amino acid residues of RecA... 

In E. coli, recA protein (352 amino acid residues product of the recA gene) plays a major role in... 

Enzymes that promote various steps of homologous recombination have been isolated from both prokaryotes and eukaryotes. In E. coli, the recB, recC, and recD genes encode the RecBCD enzyme, which has both he-licase and nuclease activities. The RecA protein pro-... 

In E. coli the synthesis of many enzymes involved in repair is regulated by the so-called SOS system. Two proteins, lexA and recA, form the working machinery of this regulatory system (fig. 26.19). Under normal conditions the lexA protein inhibits the expression of about 17 genes (the din genes), the encoded proteins of which are... 

The recombination process triggered by the initial scissions made by exoV and mediated by the recA enzyme are not sufficient for recombination between interacting chromosomes. An additional enzyme, resolvase, is required for efficient separation of the recombining chromosomes in the recA-chromosome complex. This protein is encoded by the ruvC gene in E. coli and is absolutely required for homologous recombination in the bacterium. Its effectiveness has also been demonstrated in a cell-free in vitro system. 

What is the role of the recA protein in E. coli DNA repair and in recombination What use are recA mutants in biochemical and genetic research ... 

In many recombination pathways, a DNA molecule with a free end recombines with a DNA molecule having no free ends available for interaction. DNA molecules with free ends are the common result of double-stranded DNA breaks, but they may also be generated in DMA replication if the replication complex stalls. This type of recombination has been studied extensively in E. coli, but it also takes place in other organisms through the action of proteins homologous to those of E. a)[i. Often dozens of proteins participate in the complete recombination process. However, the key protein is RecA, another member of the AAA... 

General recombination in eukaryotes is believed to be similar to the process in prokaryotes. Several eukaryotic proteins have been discovered that closely resemble in both structure and function those observed in E. coli. For example, RAD51, found in yeast, performs the same functions as RecA, i.e., repairing double stranded breaks. 

What is called DNA recombination repair is the replacement of a damaged segment of a DNA strand by a corresponding segment from an undamaged strand. In E. coli, at least, both these processes have been observed to be mediated or regulated by an enzyme (which is named RecA protein, and further identified as a 38-kDa nuclease). 

Platinum compounds without antitumor activity (17) such as t2 ons-DDP and [Pt(dien)Cl]Cl (Figure 1) covalently bind to DNA in vivo. Several studies have compared the biological effects which result when equal amounts of these three platinum compounds are fixed on DNA (typically r j 10" -10"6), Cis-DDP is 5-10 times more toxic toward E, ooli ( ) and mammalian cells (j, U.) than t2 ans-DDP, The relative toxicity is correlated with the ability of these two isomers to inhibit DNA replication (, i3, J 4). The ois isomer is repaired more efficiently by E, ooli W and is at least 750 times more mutagenic in mammalian cells (11) than the trans isomer. The compound [Pt(dien)Cl]Cl binds covalently to the DNA of E, ooli and seems not to be repaired nevertheless this compound does not inhibit DNA synthesis or kill the bacteria ( ), Repair of platinum compounds by E, ooli may be under the control of the SOS system c s-DDP induces 5-10 times more recA protein in treated E. Coli than an equal amount of trans-DPP or [Pt(dien)Cl]Cl fixed on the DNA (18), It seems that different modes of fixation on DNA are responsible for the different mutagenicity, toxicity and DNA repair of these platinum complexes. These results suggest that the antitumor activity of platinum(II) compounds may also depend on the formation of particular platinum-DNA lesions. 

Homologous recombination in E. coli is a two-step process that requires the RecA protein. In step 1, a single-stranded DNA invades the target DNA molecule and base pairs with its homologous sequence. In step 2, the heteroduplex formed in step 1 is isomerized to form a Holliday junction which is resolved by subsequent DNA cleavage and ligation reactions. 

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