Mechanical force antagonizes the inhibitory effects of RecX on RecA filament formation in Mycobacterium tuberculosis.
Bottom Line: However, applying larger forces antagonized the inhibitory effects of MtRecX, and a partially de-polymerized MtRecA filament could re-polymerize in the presence of MtRecX, which cannot be explained by previous models.Theoretical analysis of force-dependent conformational free energies of naked ssDNA and RecA nucleoprotein filament suggests that mechanical force stabilizes RecA filament, which provides a possible mechanism for the observation.As the antagonizing effect of force on the inhibitory function of RecX takes place in a physiological range; these findings broadly suggest a potential mechanosensitive regulation during homologous recombination.
Affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore.Show MeSH
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Mentions: The force-dependent conformational free energies of RecA filament and ssDNA can be calculated from their respective force-extension curves and through relations: and . were directly measured in our buffered reaction solution conditions (Figure 1B), which were used to calculate per nucleotide ssDNA. As is negative up to 90 pN, force in this range facilitates RecA polymerization by reducing the free energy cost for polymerization and is optimized in force range of 20–25 pN (Figure 4). The equilibrium between RecA polymerization and de-polymerization depends on the rates of polymerization and de-polymerization, kon and koff, respectively, through . Therefore, the effect of force on shifting the equilibrium must be through either increasing kon or decreasing koff, or both.
Affiliation: Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore Department of Physics, National University of Singapore, Singapore 117542, Singapore.