Abstract
Bacterial chromosome segregation utilizes highly conserved directional translocases of the SpoIIIE/FtsK family. These proteins employ an accessory DNA-binding domain (γ) to dictate directionality of DNA transport. It remains unclear how the interaction of γ with specific recognition sequences coordinates directional DNA translocation. We demonstrate that the γ domain of SpoIIIE inhibits ATPase activity of the motor domain in the absence of DNA but stimulates ATPase activity through sequence-specific DNA recognition. Furthermore, we observe that communication between γ subunits is necessary for both regulatory roles. Consistent with these findings, the γ domain is necessary for robust DNA transport along the length of the chromosome in vivo. Together, our data reveal that directional activation involves allosteric regulation of ATP turnover through coordinated action of γ domains. Thus, we propose a coordinated stimulation model in which γ-γ communication is required to translate DNA sequence information from each γ to its respective motor domain.
Highlights
ATP-dependent bacterial chromosome transporters mediate substrate recognition through an accessory DNA-interacting domain
We demonstrate that the ␥ domain of SpoIIIE inhibits ATPase activity of the motor domain in the absence of DNA but stimulates ATPase activity through sequence-specific DNA recognition
Our findings provide insight into the molecular mechanism of coordinated stimulation that underlies the critical step of directional activation (Fig. 7E)
Summary
ATP-dependent bacterial chromosome transporters mediate substrate recognition through an accessory DNA-interacting domain. Bacterial chromosome segregation utilizes highly conserved directional translocases of the SpoIIIE/FtsK family These proteins employ an accessory DNA-binding domain (␥) to dictate directionality of DNA transport. We show that the interactions between SpoIIIE ␥ domains are required to modulate levels of ATP turnover by the motor domain, inhibiting turnover in the absence of substrate and activating turnover through sequence-specific recognition of SRS in the permissive orientation. These data lead us to propose a coordinated activation mechanism by demonstrating how permissive recognition sequences can establish directional transport, nonpermissive sequences remain unnoticed by the translocase. Given the strong sequence and functional conservation within the SpoIIIE/FtsK family, these proteins likely employ a similar mechanism to convert directional information into chromosome translocation activity
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