Abstract
SummaryATP- and GTP-dependent molecular switches are extensively used to control functions of proteins in a wide range of biological processes. However, CTP switches are rarely reported. Here, we report that a nucleoid occlusion protein Noc is a CTPase enzyme whose membrane-binding activity is directly regulated by a CTP switch. In Bacillus subtilis, Noc nucleates on 16 bp NBS sites before associating with neighboring non-specific DNA to form large membrane-associated nucleoprotein complexes to physically occlude assembly of the cell division machinery. By in vitro reconstitution, we show that (1) CTP is required for Noc to form the NBS-dependent nucleoprotein complex, and (2) CTP binding, but not hydrolysis, switches Noc to a membrane-active state. Overall, we suggest that CTP couples membrane-binding activity of Noc to nucleoprotein complex formation to ensure productive recruitment of DNA to the bacterial cell membrane for nucleoid occlusion activity.
Highlights
While ATP and GTP switches are ubiquitous in biology, CTP switches have rarely been identified but may be more widespread than previously appreciated
The conformation of the N-terminal 10 AA sequence of Noc in a membrane-bound state is not yet known, our results suggest that the properties of these amino acids are fine-tuned for membrane-binding activity
We provide evidence that (1) CTP is required for Noc to form the NBS-dependent nucleoprotein complex, and (2) CTP binding switches Noc from a membrane-inactive auto-repressed state to a membrane-active state
Summary
While ATP and GTP switches are ubiquitous in biology, CTP switches have rarely been identified but may be more widespread than previously appreciated. The ParB clamp self-loads at parS, spreads by sliding to neighboring DNA while still entrapping DNA (Jalal et al, 2020a; Soh et al, 2019). The result is the formation of a higher-order nucleoprotein complex with multiple ParB-CTP clamps entrapped in the vicinity of the parS locus. The higher-order nucleoprotein complex stimulates the ATPase activity of ParA, a partner of ParB, driving the segregation of replicated chromosomes to daughter cells (Hwang et al, 2013; Jalal and Le, 2020; Lim et al, 2014; Vecchiarelli et al, 2012, 2013, 2014)
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