An actin-like filament fromClostridium botulinumexhibits a novel mechanism of filament dynamics

AbstractHere, we report the discovery of a ParM protein fromClostridium botulinum(CBgs-ParM), which forms a double-stranded polar filament. CBgs-ParM shares many similarities in its basic filament architecture with actin, however, Pi release after nucleotide hydrolysis induces a large lateral strand shift of ~2.5 nm. We identified the ParR (CBgs-ParR) that acts as a nucleation factor in the initial stage of polymerization, similar to ParR fromEscherichia coliplasmid R1. CBgs-ParR also functions as a depolymerization factor, probably by recognizing the structural change in the CBgs-ParM filament after Pi release. Comparison with CBH-ParM, another ParM fromClostridum botulinum, showed that subunit-subunit interacting regions largely differ, preventing co-polymerization, implying a selection pressure in evolution to prevent interference between different ParMRC systems.