Disease relevance of repA

• It was observed that when the repA and repB genes were expressed in Escherichia coli, a strong ori binding activity was generated in the host cells [1].
• A derivative of pKL1, pKL1Km, in which the transposon was restricted to a small 350-bp region, was stably maintained in Shigella, Salmonella, Serratia, and Citrobacter species and its replication was polA independent. pKL1 encoded only a single protein, RepA (Mr 17960), which specifically bound to pKL1 DNA [2].
• RepA protein of the bacteriophage N15 exhibits activity of DNA helicase [3].

High impact information on repA

• The RepA protein of plasmid pSC101 controls Escherichia coli cell division through the SOS response [4].
• The effects of RepA excess are prevented by introducing a surfeit of RepA binding sites [4].
• We show that delayed cell division occurs by RepA-mediated induction of the SOS response and can be reversed by over-expression of the host DNA primase, DnaG [4].
• Here we report a novel mechanism by which the pSC101 plasmid also can detect an imbalance between the cellular level of its replication protein, RepA, and plasmid-borne RepA binding sites to inhibit bacterial DNA replication and delay host cell division when RepA is in relative excess [4].
• In the mycobacterial plasmid pAL5000 replication region, the replication genes repA and repB are organized in an operon [5].

Biological context of repA

• The cop region also harbors a region of plasmid incompatibility, inc, encompassing a stem-loop structure, the repA promoter, Prep, as well as two distinct RepA binding sites, BD-1 and BD-2 [6].
• Both RepA binding sites were required to maintain incompatibility and effective pKL1 replication [6].
• RepA protected a 68-bp region of the origin of replication of pMU720 [7].
• The nucleotide sequence analysis revealed the presence of an open reading frame encoding a putative 317 amino acids protein homologous to replication proteins RepA [8].
• Residues K42, E76, D77, D139 and H178, proposed to play key roles in catalyzing the hydrolysis of NTPs, are essential for RepA activity [9].

Analytical, diagnostic and therapeutic context of repA

• Incompatibility was shown to be due to the titration of RepA at the cop locus but could be easily overridden by excess RepA [6].
• To elucidate the oligomerization properties of RepA in solution, RepA was expressed in E. coli; purified by ion exchange and hydrophobic chromatography; and examined in solution by spectrapolarimetry, light scattering, sedimentation velocity, and equilibrium ultracentrifugation [10].
• Sequence analysis of pHS649 identified a putative RepA protein with 48% similarity to the RepA protein of Escherichia coli plasmid pKL1 [11].

References