ECs1669

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..These results are consistent with FtsZ as the target of MinCD and confirm that this inhibitor prevents Z-ring assembly...

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..DivIVA therefore appears to be a bifunctional protein with distinct roles in division-site selection and chromosome segregation...

..A model is presented in which the requirements for the MinD ATPase contribute spatial and temporal inputs that provide the mechanistic basis for the oscillation...

..Recent studies have shown that MinE, previously thought to form a static ring near the division site at the midcell position, actually joins MinC and MinD in their rapid oscillation between the cell poles...

..5 A, and diffract to 3.0 A resolution. The asymmetric units each contain one molecule of MinD, giving a crystal volume per protein mass (V(M)) of 3.0 A(3) Da(-1) and a solvent content of 59.0%...

..These results provide further evidence that the negative topological effect of nucleoids in cells lacking MukB is partially but not totally suppressed, and that the absence of the Min system allows more promiscuous Z ring formation...

..We have interpreted the polarized orientation of the studied gene regions as a consequence of the mode of DNA segregation...

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..The individual function of orf1 or the function of both orf1 and truncated orf2 seems to induce particular phenotypes or properties in strain BalA1...

..These results indicate that MinCD blocks the assembly of the septation machinery at a later step than SulA, at the stage at which FtsA is added to the FtsZ ring...

..The MinCDE system regulates the position of the division plane in rod-shaped bacteria. New results from Escherichia coli provide insight into how this operates by showing that MinE stimulates the ATPase activity of MinD...

..This review summarizes and integrates these insights...

..On time average, MinC concentration is highest at the poles, forcing FtsZ assembly to the center. The mechanism is self-organizing and does not require any other hypothetical topological determinant...

..We conclude that membrane binding by MinD involves penetration of the hydrophobic residues within the C-terminal amphipathic helix into the hydrophobic interior of the bilayer...

..The sequential interaction of MinD with these two proteins, which is dictated by the membrane, is critical to the oscillatory mechanism involved in spatial regulation of division...

..We suggest a model in which the ATP-dependent dimerization of MinD affects the conformation of the C-terminal region, a potential amphipathic helix, triggering membrane binding...

..These results suggest that MinE induces a conformational change in MinD bound to the bilayer that results in the release of MinC. Also, it is argued that binding of MinD to the membrane activates MinC...

..Taken together, our results suggest that reversible MinD assembly modulated by MinE underlies the dynamic processing of positional information in E. coli to identify precisely the nascent site for cell division...

..A model is proposed whereby the membrane-targeting motif mediates the rapid cycles of membrane attachment-release-reattachment that are presumed to occur during pole-to-pole oscillation of MinD in E. coli...

..Finally, in round E. coli cells, GFP-MinDNg appeared to move in a plane parallel to completed septa. This pattern of movement is predicted to be similar in gonococcal cells, which also divide in alternating perpendicular planes...

..The results suggest a multistep mechanism for the activation of MinC-mediated division inhibition by either MinD or DicB and further expand the number of properties that can be ascribed to the Min proteins...

..A new model for the spatial control of division planes by the Min system in round cells is proposed...

..The other mutations may identify a surface of MinD involved in its interactions with DivIVA and a possible mechanism for control of MinD by DivIVA...

..Our model spontaneously generates protein oscillations in good agreement with experiments. We explore the oscillation stability, frequency, and wavelength as a function of protein concentration and bacterial length...

..These data infer that gonococci regulate their cell division in response to different environments...

..This finding correlates well with the previously observed oscillatory movement of MinC and MinD in short and long cells...

..The fusion of these two independent domains is required to achieve topological regulation of Z ring assembly...

..Recent work on the bacterium Escherichia coli has shown that correct placement of the cell division site at the midcell position occurs by a combination of selection against potential polar sites and selection of the midcell site...

..tularensis homologue of minD had been interrupted. Western immunoblot analysis confirmed the presence of a MinD homologue in F. tularensis WT and KEM21, and demonstrated its absence in KEM7...

..A surprisingly large fraction of the ORFs (at least six out of 17) in the centromeric region are apparently involved in RNA or DNA binding...

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..minB is located at min 25.6, between purB (min 25.2) and dadR (min 25.8). The mapping was facilitated by the use of insertion zcf-236::Tn10, which is inserted at min 25.4...

..Abnormal DNA distribution and production of anucleate rods suggest that the Min product(s) could be involved in DNA distribution...

..The results indicate that minB is a complex locus whose expression must be maintained within certain limits to maintain the normal pattern of localization of the division septum...

..Natl. Acad. Sci. USA 87:1129-1133, 1990), these results provide evidence that, in addition to promoting division inhibition with MinD, protein MinC acts in concert with DicB to inhibit division by a second, MinD-independent process...

..It was shown that SulA inhibits cell division independently of MinCD...

..We conclude that the min+ function is only to prevent septation only at polar sites; the placement of internal cell division sites must obey strict rules, which are the same in minB and wild-type cells...

..As a consequence, these cells divide between nucleoid and cell pole, resulting in minicell and (sometimes) in anucleate cell formation...

..DNA-less cell formation in dnaX(Ts), dnaX(Ts) sfiA, and the minB minicell-forming mutant is accompanied by a local increase in peptidoglycan synthesis at the constriction site...

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..The results obtained call for a re-evaluation of the role of the MinB system in the E. coli cell cycle, and of the concept that limiting quanta of cell division factors are regularly produced during the cell cycle...

..We suggest that the retarded nucleoid segregation observed in min mutants is the result of this coupling in cells with a perturbed pattern of nonpolar divisions...

..Finally, the branched cells are compared with bacteria that normally branch, and probable causes for branching in E. coli are discussed...

..In addition, analysis of min mutants demonstrated that FtsZ ring formation was also associated with minicell formation, indicating that all septation events in E. coli involve the FtsZ ring...

..Studies with the isolated N-terminal and C-terminal MinE domains indicated different roles for the two MinE domains in the redistribution of membrane-associated MinD...

..Thus, MinC is positioned by the other Min products, but in a dynamic manner so that it is in position to inhibit Z ring assembly away from midcell...

..A model is proposed in which both the inhibitory effect of the nucleoid and the regulation by MinCDE ensure that cells divide precisely at the midpoint...

..coli Mrp protein and contains representants of the three domains of life. The conservation of MinD-like proteins in the three domains of life suggests that these proteins play a central role in cellular metabolism...

..When grown in rich medium, greater than 50% of the minCD mutant cells had multiple FtsZ rings, indicating significant differences in regulation of FtsZ ring formation based on growth medium...

..Remarkably, this mechanism of DivIVA action is completely different from that of the equivalent protein MinE of Escherichia coli, even though both systems operate via the same division inhibitor MinCD...

..We propose that the MinCD complex plays an important role in asymmetric septum formation during sporulation of B. subtilis cells...

..We also report that high-level synthesis of MalE disturbs nucleoid partitioning...

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..However, interactions were observed among various members of the Min system, and MinE was found to reduce the interaction between MinC and MinD. The implications of these findings for cell division are discussed...

..However, neither minC nor minD function was absolutely required for sporulation and, by implication, for asymmetric septum formation...

..Moreover, E. coli cells carrying the divIVB region on a low-copy-number plasmid produce minicells, suggesting that a product of this locus may retain some function across species boundaries...

..The results suggest a mechanism whereby MinD is required both to pilot MinC to the cell poles and to constitute a functional division inhibitor...

..The study of bacterial cell division is important not only because it is a basic cellular process that needs to be understood, but also because cytokinesis is an important potential target of antimicrobials. ..

..Finally, the new program has been based on our track record in which eleven investigators supported by the previous COBRE have secured a total of 16 extramural grants. Eight of the eleven have secured 12 NIH grants. ..

..It has great similarity to tubulin but is also quite distinct. As a result it should prove to be a useful, novel target for antimicrobial therapy. ..

..The results of this proposed research are expected to provide a more complete understanding of the molecular mechanisms of cell division, and should facilitate the isolation of new and better antimicrobial drug targets. ..

..Finally, the new program has been based on our track record in which eleven investigators supported by the previous COBRE have secured a total of 16 extramural grants. Eight of the eleven have secured 12 NIH grants. ..

..The study of bacterial cell division is important not only because it is a basic cellular process that needs to be understood, but also because cytokinesis is an important potential target of antimicrobials. ..

..PUBLIC HEALTH RELEVANCE: This project investigates the molecular mechanism of bacterial cell division. The highly conserved proteins in the cell division apparatus represent novel targets for new therapeutics. ..

..MreB-- To isolate the MreB and Min cytoskeletal-like structures, to characterize proteins that interact with MreB, and to define the behavior of the MreB cytoskeletal-like structures during the course of the cell cycle. ..

..Understanding the molecular mechanisms that normally control cell division will help identify why they fail during oncogenesis, leading to the aberrant divisions and rapid proliferation characteristic of cancer cells. ..

..To characterize new minicell mutants that map outside of the minCDE locus and determine whether any of them code for the topological targets for MinD and MinE localization. ..

..Understanding the molecular mechanisms that normally control cell division will help identify why they fail during oncogenesis, leading to the aberrant divisions and rapid proliferation characteristic of cancer cells. ..

..4. To determine whether the residual division sites that are present at the cell poles play a role in the generation of future division sites within the cell. ..