Influence of the C-Terminal Tail of RecA Proteins from Alkaline pH-Resistant Bacterium Deinococcus Ficus

Deinococcus ficus CC - FR2 - 10T , resistant to ultraviolet, ionizing radiation, and chemicals which may cause DNA damage, was identified in Taiwan. The expression level of D. ficus RecA, which has 92% sequence identity with Deinococcus radiodurans ( Dr. ) RecA, will be upregulated upon UV radiation. Multiple sequence alignment of RecA proteins from bacteria belonging to Escherichia coli and the Deinococcus genus reveals that the C-terminal tail of D. ficus RecA is shorter and contains less acidic residues than E. coli RecA. D. ficus RecA exhibits a higher ATPase activity toward single-stranded (ss) DNA and efficiently promotes DNA strand exchange that a filament is first formed on ssDNA, followed by uptake of the double-stranded (ds) substrate. Moreover, D. ficus RecA exhibits a pH-reaction profile for DNA strand exchange similar to E. coli Δ C17 RecA. Later, a chimera D. ficus C17 E. coli RecA with more acidic residues in the C-terminal tail was constructed and purified. Increased negativity in the C-terminal tail makes the pH reaction profile for Chimera D. ficus C17 E. coli RecA DNA strand exchange exhibit a reaction optimum similar to E. coli RecA. To sum up, D. ficus RecA exhibits reaction properties in substrate-dependent ATPase activity and DNA strand exchange similar to E. coli RecA. Our data indicate that the negativity in the C-terminal tail plays an important role in the regulation of pH-dependent DNA strand exchange activity.