SulA inhibits assembly of FtsZ by a simple sequestration mechanism.
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We have investigated the inhibition by SulA of the assembly of Escherichia coli FtsZ. Using quantitative GTPase and fluorescence assays, we found that SulA inhibition resulted in an increase in the apparent critical concentration for FtsZ assembly. The increase in apparent critical concentration was always less than the total amount of SulA added, suggesting that the association of SulA and FtsZ was of modest affinity. Isothermal titration calorimetry gave a value of 0.78 μM for the dissociation constant of the FtsZ-SulA complex, similar in magnitude to the 0.72 μM critical concentration of FtsZ protofilament assembly at steady state. We modeled the reaction as an equilibrium competition between (a) FtsZ subunits assembling onto protofilaments or (b) binding SulA. When FtsZ was assembled in GMPCPP or in EDTA, the inhibition by SulA was reduced. The reduced inhibition could be explained by a 3- and 10-fold weaker binding of SulA to FtsZ. The mutant D212G, which has no GTPase activity and therefore minimal subunit cycling, was shown here to assemble one-stranded protofilaments, and the assembly was blocked by SulA. We also assayed the SulA and FtsZ proteins from Pseudomonas. The SulA inhibition was stronger than with the E. coli proteins, and the model indicated a 5-fold higher affinity of Pseudomonas SulA for FtsZ.
Escherichia coli Proteins
Published Version (Please cite this version)10.1021/bi201669d
Publication InfoChen, Yaodong; Erickson, Harold Paul; & Milam, Sara L (2012). SulA inhibits assembly of FtsZ by a simple sequestration mechanism. Biochemistry, 51(14). 10.1021/bi201669d. Retrieved from https://hdl.handle.net/10161/16456.
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James B. Duke Professor of Cell Biology
Cytoskeleton: It is now clear that the actin and microtubule cytoskeleton originated in bacteria. Our major research is on FtsZ, the bacterial tubulin homolog, which assembles into a contractile ring that divides the bacterium. We have studied FtsZ assembly in vitro, and found that it assembles into thin protofilaments (pfs). Dozens of these pfs are further clustered to form the contractile Z-ring in vivo. Some important discoveries in the last ten years include: &bul