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The three-dimensional structure of septum site-determining protein MinD from Pyrococcus horikoshii OT3 in complex
1Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
Background:
In Escherichia coli, the cell division site is determined by the cooperative activity of min operon products MinC, MinD, and MinE. MinC is a nonspecific inhibitor of the septum protein FtsZ, and MinE is the supressor of MinC. MinD plays a multifunctional role. It is a membrane-associated ATPase and is a septum site-determining factor through the activation and regulation of MinC and MinE. MinD is also known to undergo a rapid pole-to-pole oscillation movement in vivo as observed by fluorescent microscopy.
Results:
The three-dimensional structure of the MinD-2 from Pyrococcus horikoshii OT3 (PH0612) has been determined at 2.3 A resolution by X-ray crystallography using the Se-Met MAD method. The molecule consists of a beta sheet with 7 parallel and 1 antiparallel strands and 11 peripheral alpha helices. It contains the classical mononucleotide binding loop with bound ADP and magnesium ion, which is consistent with the suggested ATPase activity.
Conclusions:
Structure analysis shows that MinD is most similar to nitrogenase iron protein, which is a member of the P loop-containing nucleotide triphosphate hydrolase superfamily of proteins. Unlike nitrogenase or other member proteins that normally work as a dimer, MinD was present as a monomer in the crystal. Both the 31P NMR and Malachite Green method exhibited relatively low levels of ATPase activity. These facts suggest that MinD may work as a molecular switch in the multiprotein complex in bacterial cell division.
Insights
The structure of Pyrococcus horikoshii MinD reveals its similarity to nucleotide triphosphate hydrolases. Despite low ATPase activity, MinD may function as a molecular switch in bacterial cell division.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- MinD is a key protein in bacterial cell division in Escherichia coli, regulating septum formation.
- MinD is a membrane-associated ATPase involved in activating and regulating MinC and MinE proteins.
- MinD exhibits dynamic pole-to-pole oscillation in vivo.
Purpose of the Study:
- To determine the three-dimensional structure of MinD-2 from Pyrococcus horikoshii OT3 (PH0612).
- To investigate the structural basis for MinD's ATPase activity and its role in cell division.
Main Methods:
- X-ray crystallography at 2.3 A resolution using the Se-Met MAD method.
- 31P NMR and Malachite Green assay to assess ATPase activity.
Main Results:
- The crystal structure of MinD-2 revealed a beta sheet and alpha helices, containing a nucleotide binding loop with ADP and magnesium.
- MinD-2 crystallized as a monomer, unlike related dimeric proteins.
- ATPase activity assays showed relatively low levels of activity.
Conclusions:
- MinD shares structural similarities with the nitrogenase iron protein family.
- The monomeric state and low ATPase activity suggest MinD acts as a molecular switch in the bacterial cell division complex.