FtsZ est une protéine indispensable à la multiplication bactérienne. Elle est une cible thérapeutique intéressante dans la recherche de nouvelles molécules antibiotiques. FtsZ se polymérise en filaments qui s'assemblent en une structure : le "Z-ring". FtsZ est une GTPase qui lie et hydrolyse le GTP, pour donner un GDP. L'objectif de cette thèse est d'étudier par dynamique moléculaire l'influence du nucléotide GTP/GDPet de l'ion Mg2+ sur les changements conformationnels ainsi que sur la dynamique de FtsZ. Une première approche a consisté à étudier le monomère de FtsZ. Ces simulations n'ont révélé que peu d'influence de la nature du nucléotide sur la structure. Cependant, la présence de l'ion Mg2+ dans la poche du nucléotide provoque des changements conformationnels de FtsZ-GDP ainsi qu'un mouvement du GDP au sein du site actif. Dans la deuxième partie, l'étude du dimère de FtsZ a permis d'explorer en plus de l'influence du nucléotide, celle de l'état de protonation des chaînes latérales de trois acides aspartiques (Asp72A, Asp235B et Asp238B) présents à l'interface. Les résultats ont démontré que les chaînes latérales des Asp235B et 238B doivent être protonées pour que le dimère FtsZ-GTP-Mg soit stable. D'autre part, dans le dimère FtsZ-GDP-Mg en solution, la protonation des Asp 235B et 238B provoque une courbure du dimère avec un éloignement des monomères et un déplacement du GDP à l'interface. Cette séparation ressemble à un début de dépolymérisation. le GDP et l'ion Mg2+ provoquent des déformations du monomère et du dimère de FtsZ. Une étude approfondie de la protonation des résidus de l'interface permettrait de mieux comprendre la polymérisation et l'hydrolyse du GTP. / Most bacteria use a prokaryotic protein, FtsZ to divide. FtsZ polymerizes and assembles into the "Z-ring". FtsZ is a GTPase that can bind and hydrolyze GTP. The aim of this study is to explore FtsZ structure and dynamics as a function of GTP/GDP. First, we performed molecular dynamics simulations of FtsZ monomer to study the influence of GTP/GDP and Mg2+ ion on its structure and dynamics. These simulations revealed that the nature of the nucleotide doesn't affect the structure of FtsZ. However, the presence of the magnesium ion in the nucleotide-binding pocket causes conformational changes of FtsZ monomer when bound to GDP. The Mg2+ ion induces a dynamical motion of the GDP within the nucleotide-binding site. In the second part, we studied the influence of the nucleotide on FtsZ dimer by molecular dynamics. These simulations also allowed to investigate the influence of the protonation state of three aspartic acids sidechains (Asp72A, Asp235B and Asp238B). These Asp are present at the dimer interface. We demonstrated that the sidechains of two aspartic acids Asp235B and Asp238B have to be protonated during polymerization of FtsZ-GTP-Mg dimer. On the other hand, when the sidechains of Asp235B and Asp238B are protonated, FtsZ-GDP-Mg dimer gets curved and the two monomers are separated. We also observed a GDP motion at the dimer interface. This separation looks like the beginning of depolymerization. The association of GDP with the Mg2+ ion causes important conformational changes of FtsZ monomer and dimer. An in-depth study of the protonation state of residues at the interface would allow a better understanding of polymerization of FtsZ and GTP hydrolysis.

<p>Bacterial tubulin homolog FtsZ assembles straight protofilaments (pfs) that form the scaffold of the cytokinetic Z ring. These pfs can adopt a curved conformation forming a miniring or spiral tube 24 nm in diameter. Tubulin pfs also have a curved conformation, forming 42 nm tubulin rings. We have previously provided evidence that FtsZ generates a constriction force by switching from straight pfs to the curved conformation, generating a bending force on the membrane. In the simplest model the membrane tether, which exits from the C terminus of the globular FtsZ, would have to be on the outside of the curved pf. However, it is well established that tubulin rings have the C terminus on the inside of the ring. Could FtsZ and tubulin rings have the opposite curvature? In the present study we explored the direction of curvature of FtsZ rings by fusing large protein tags to the N or C terminus of the FtsZ globular domain. FtsZ with a protein tag on the N terminus did not assemble tubes. This was expected if the N terminus is on the inside, because the protein tags are too big to fit in the interior of the tube. FtsZ with C-terminal tags assembled normal tubes, consistent with the C terminus on the outside. The FN extension was not visible in negative stain, but thin section EM gave definitive evidence that the C-terminal tag was on the outside of the tubes. This has interesting implications for the evolution of tubulin. It seems likely that tubulin began with the curvature of FtsZ, which would have resulted in pfs curving toward the interior of a disassembling MT. Evolution not only eliminated this undesirable curvature, but managed to reverse direction to produce the outward curving rings, which is useful for pulling chromosomes.</p> / Dissertation

Prokaryotic cell division is one of the most fundamental processes in biology, but the dynamics and mechanics are far from being understood. In many bacteria, FtsZ, a tubulin homologue assembles into a ring-like structure – Z-ring at precisely the middle of the cell. This accurate site selection is dependent on the Min proteins. Min D and MinE self-organise into waves in vitro, and oscillate pole to pole in vivo. MinC is thought to couple the Min oscillations to FtsZ by direct interaction. The mechanism of inhibitory action of MinC on FtsZ assembly is not known. Critical to the understanding of regulation of FtsZ by MinC and other proteins and its probable role in force generation is the organisation, structure and the dynamics of the Z-ring. Current models of the FtsZ filament organization in the Z-ring argue between two different structures – (i) short overlapping protofilaments with lateral interactions and (ii) few long annealed protofilaments with or without lateral contacts. Our observations of the characteristics of polymerization and turnover studies using fluorescence microscopy suggest that the FtsZ filament is a continuous and irresolute bundle. The results are consistent with a structure where the turnover happens throughout, and any specialised structure resulting in a GTP cap like structure can be ruled out. We show that the turnover rates and hydrolysis rates are similar arguing for a model in which subunit leaves as soon as it hydrolyses GTP. On the basis of crystal structures, we cloned the N-terminal of FtsZ, which acts as a C-terminal end capping fragment and is able to interact with monomers. The end-capping fragment, NZ can disassemble the FtsZ polymers, without influencing the GTPase activity, offering a comparable standard for the activity of MinC. On the basis of our observations, we propose a model on how MinC can disassemble FtsZ polymers. Furthermore, our data shows that the Min CDE system is sufficient to cause spatial regulation of FtsZ provided FtsZ is dynamic. How the Z-ring takes the form of a functional helical or ring-like structure remains unclear. Extensive modelling approaches have tried to explain the ring formation and force generation. Previous studies have qualitatively shown bending of liposome membranes by FtsZ filaments. We hypothesised that the presumably intrinsically curved filaments should respond to pre-curved substrates, and the alignment should be quantifiable. This should ascertain whether or not FtsZ has intrinsic curvature and/or actively induces any force. Thus, we investigated how FtsZ filaments respond to a range of curvatures, which mimic different stages of the division process. Our results show that the FtsZ filaments possess intrinsic curvatures as well as spontaneous twist. This facilitates the formation of Z-ring by utilizing geometrical cues. Our results are in agreement with consistent helical FtsZ polymers observed in vivo by Cryo-EM or super resolution microscopy. The alignment of filaments over a range of curvature suggests that the filaments have considerable flexibility, which strongly suggests reconsidering possible mechanisms of force generation. Moreover, the developed assay constitutes a valuable platform to further study proteins involved in modifying curvature of FtsZ filaments. In summary, by reconstituting the FtsZ filament in vitro, we have elucidated the nature of FtsZ filaments. The dynamics of FtsZ filaments allows them to be inhibited by MinC, thus cooperating with the Min waves. The presence of intrinsic curvature and twist facilitates their formation into a ring necessary for the cell to carry out cytokinesis.

FtsZ, the principal cell-division protein, polymerizes in GTP-dependent manner in vitro (Bramhill and Thompson, 1994; Mukherjee and Lutkenhaus, 1994; Rivas et al., 2000). FtsZ polymerization at the mid-cell site of bacterium leads to formation of a guiding scaffold, the Z-ring, for bacterial cytokinesis (Bi and Lutkenhaus, 1991; Sun and Margolin, 1998). GTP-induced polymerization process of FtsZ can be monitored in vitro Using 90º light scattering (Mukherjee and Lutkenhaus, 1999) and polymers formed can be visualized using transmission electron microscopy (Lu and Erickson, 1998) or quntitated in terms of the amount of FtsZ polymer pelleted during ultracentrifugation (Mukherjee and Lutkenhaus, 1998). The research work presented in this thesis focused on structure-function correlative analysis of Mycobacterium tuberculosis FtsZ(MtFtsZ0 and FtsZ proteins of Mycobacterium leprae (M1FtsZ), Mycobacterium smegmatis(MsFtsZ), and Streptomyces coelicolor (ScFtsZ) (as it is from Actinomycetes family to which mycobacteria belong) in vitro. It was initiated with investigation on the biochemical properties of Mycobacterium leprae FtsZ (M1FtsZ) in vitro. In comparison with those of MtFtsZ. Subsequently, the role of C-terminal stretch of amino acid residues of MtFtsZ in polymerization was investigated. Finally, a comparative analysis of the biochemical properties of MtFtsZ, MsFtsZ, and ScFtsZ was carried out in order to find out whether a correlation exists between the time taken by the FtsZ of a bacterium to polymerise and the generation time of the organism. The thesis is presented in five chapters. First Chapter gives an exhaustive introduction on the structure-function aspects of FtsZ. Second Chapter deals with materials used in this research work and details of various experimental methods [cloning and expression of FtsZ (White et. Al., 2000), decision and point mutagenesis, preparation of His-tag free MtFtsZ and M1FtsZ by thrombin cleavage method, 90º light scattering (Mukherjee and Lutkenhaus, 1999), White, et al., 2000), transmission electron microscopy (Lu and Erickson, 1998), pelleting assay for polymeric FtsZ (Mukherjee and Lutkenhaus, 1998), GTP-binding by UV-crosslinking (RayChaudhuri and Park, 1992; de Boer et al.,) GTPase assay(RayChaudhuri and Park, 1992); de Boer et al., 1992), Circular Dichroism (Saxena and Wetlaufer, 1971) and ANS fluorescence emission spectroscopy (Semisotnov, et al., 1991)]. The Chapters three to five contain all the data related to the research work, the outlines of which are given below. Chapter 3. Biochemical Characterisation of FtsZ Protein of Mycobacterium leprae In Comparison with the Biochemical Properties of FtsZ Protein of Mycobacteriulm tulberculosis In Vitro The major finding in this part of thesis work is on the demonstration that single reciprocal point mutation partially revives polymerization-inactive M1FtsZ and Inactivates polymerization-active MtFtsZ in vitro. In brief, soluble, recombinant M1FtsZ did not show detectable polymerization in vitro, in contrast to MtFtsZ, which showed appreciable polymerization, under standard conditions, when monitored using 90º light scattering assay and transmission electron microscopy. This was a surprising result, as M1FtsZ and MtFtsZ has 96% protein sequence identity. Mutation f T172 in the N-terminal domain of M1FtsZ to A172, as it exists in MtFtsZ, showed dramatic levels of polymerization in vitro. Reciprocal mutation of A172 in MtFtsZ to T172, as it exists in M1FtsZ, abolished polymerization in vitro. Further, M1FtsZ showed weak GTPase activity, in contrast to MtFtsZ, which showed appreciable GTPase activity. While T172A mutation enhanced GTPase activity of MtFtsZ in vitro. Circular dichroism spectroscopy and ANS fluorescence emission spectroscopy showed that there were no major secondary or tertiary structural changes in these point mutants. These observations demonstrate that the residue at position 172 plays a critical role in the polymerization of M1FtsZ and MtFtsZ, without appreciably affecting their respective GTpPase activity. Further, this result might have implications on evolution of a slow polymerizing FtsZ in slow growing bacteria. Further details of evolution related questions are addressed in Chapter 5. Chapter 4. Role of Carboxy Terminal Residues in the Biochemical Properties of FtsZ Protein of Mycobacterium tuberculosis In Vitro The major finding in this part of thesis work is the demonstration that the C-terminal end residues are critically required for polymerization of MtFtsZ in vitro, which is in direct contrast to the dispensability of C-terminal residues of Escherichia coli FtsZ(EcFtsZ), Bacillus subtilis FtsZ (BsFtsZ), and Pseudomonas aeruginosa (PaFtsZ) for polymerization. FtsZ protein from several bacterial species namely, Methanococcus jannaschii (MjFtsZ), Bacillus subtillis(BsFtsZ), Pseudomonas aeruginosa (PaFtsZ), and Aquifex aeolicus (AaFtsZ) (Lowe and Amos, 1998; Oliva et al., 2007), and Mycobacterium tuberculosis H37Rv (mtFtsZl Leung et al., 2004), whose crystal structures have been solved so far, were found to possess an N-terminal domain and a C-terminal domain that were connected to each other through a helix. The extreme C-terminal portion of all these FtsZ proteins is constituted by an unstructured tail (Lowe and Amos, 1998; Oliva et al., 2007l Leung et al., 2004), which is not found in the respective crystal structure of the protein. We examined whether C-terminal residues of soluble recombinant FtsZ of Mycobacterium tuberculosis (mtFtsZ) have any role in MtFtsZ polymerization in vitro. Deletion of C-terminal 66 residues (313-379) was found to abolish polymerization. Replacement of the C-terminal 66 residues with the extreme C-terminal 13-residue stretch (DDDDVDVPPFMRR) did not restore polymerization. Although the terminal R in DDDDVDVPPFMRR is dispensable for full-length MtFtsZ polymerization, the terminal R in DDDDVDVPPFMR is indispensable for polymerization. Neither replacement of this R, in the terminal R deletion mutant DDDDVDVPPFMR, with K/H/D/A residues enabled polymerization. GTP binding and GTPase activities of the mutants were partially affected. The indispensable nature of C-terminal residues for MtFtsZ polymerization in vitro is contrary to the dispensability of the equivalent extreme C-terminal residues of Escherichi coli, Pseudomonas aeruginosa, and Bacillus subtilis FtsZ (Wang et. Al., 1997; Cordell et al., 2003; Singh et al., 2007) for in vitro polymerization. The essentiality of C-terminal extreme residues of BtFtsZ for polymerization offers direction to design anti MtFtsZ polymerization agents. Chapter 5. An attempt to find correlation between Biochemical properties of FtsZ and Generation Time of the Bacterium The clue that there might be a correlation between FtsZ polymeristion and generation time of the bacterium came from the observation mentioned in chapter 3. The presence of polymerization-aversive T172 in the FtsZ of extremely slow-growing M. leprae 913.5 days generation time, Levy, 1970) and polymerization-favouring A172 in the FtsZ of M. tuberculosis(18hrs generation time, Patterson and Youmans, 1970). For a bacterium, which has short generation time, it might be conducive to have an FtsZ that will also polymerise fast. Conversely, for a bacterium, which has long generation, it might be conducive to have an FtsZ molecule that will polymerise slow. In this respect, a preliminary comparative study was carried out between the generation time of bacterial species, E. coli, Mycobacterium smegmatis, Streptomyces coelicolor, M leprae, and M. tuhberculosis and their respective FtsZ (EcFtsZ, MsFtsZ, M1FtsZ and MtFtsZ). Detailed biochemical characterization of EcFtsZ and MtFtsZ has already been reported in the literature. In this thesis work, biochemical characterisation of M1FtsZ(Chapter 3), ScFtsZ and MsFtsZ (in this Chapter) were carried out. E. coli, which has a generation time of 18-55 min(labrum, 1953), possesses FtsZ (EcFtsZ) that reaches steady state of polymerization in about 10 sec under standard conditions in vitro (Beamhill and Thompson, 1994), using 90º light scattering assay (Mukherjee and Lukenhaus, 1999). On the other hand, M. tuberculosis, which has a generation time of 18hrs in vivo (Patterson and Youmans, 1970) and 24 hrs in vitro (Hiriyanna and Ramakrishnan, 1986) possesses FtsZ (MtFtsZ) that reaches steady state of polymerization in about 6 min post-addiction of GTP in vitro (White et al., 2000). Further, M. leprae, which takes 13.5 days tp divide once in vivo (levy, 1970), possesses an FtsZ (M1FtsZ) that does not even show polymerization under standard conditions in vitro (Chapter 3 of this thesis). The organisms Mycobacterium smegmatis and Streptomyces coelicolor have generation times that fall in between those of the other three organisms mentioned above. While M. smegmatis divides once in 2-3 hrs (Husson, 1998), S. coelicolor has a variable generation time depending on growth condition, which can be as fast as once in 2.31 hours, depending upon growth conditions (Cox, 2004). We found ScFtsZ and MsFtsZ takes around 4 min to reach polymerization saturation after addition of GTP, EcFtsZ( 10 sec), MtFtsZ (10 min) and M1FtsZ (dose not polymerise in vitro) seem to indicate that there exists a correlation between polymerization saturation after addition of GTP, EcFtsZ (10sec), MtFtsZ (10 min) and M1FtsZ (does not polymerise in vitro) seem to indicate that there exists a correlation between polymerization saturation time and the generation time of the respective bacterium. But when we compared polymerization time of ScFtsZ and MsFtsZ (4 min both case) with MtFtsZ ( 6 min), we found that there is no linear correlation with generation time of these bacteria and the time taken by their FtsZ to reach steady state of polymerization. Many more bacterial FtsZ proteins need to be characterized to conclusively state wthether there exist a correlation between generation time of bacteria and the time taken for their FtsZ to reach steady state of polymeristion. Such correlation would simply reveal the fact that the primary structure of an FtsZ protein might have evolved to suit the generation time of the bacterium.

Chloroplasts are the powerhouses of plants and also perform important storage functions. Chloroplast division is an essential process that involves proteins that are conserved from prokaryotic fission and proteins evolved in eukaryotes. Due to their endosymbiotic origin, the division machineries of chloroplasts and all plastids share some core similarities with the bacterial division apparatus, but during evolution some prokaryotic components of the division machinery were not conserved and some novel components evolved to fulfill new functions. The components of the division apparatus and their interactions are being elucidated, but relatively little is known about the mechanism and dynamics of the first protein families to localize to the division site, FtsZ1 and FtsZ2. This work details a thorough investigation of the biochemical characterization of Arabidopsis thaliana FtsZ proteins and begins to determine the mechanism of FtsZ assembly. To achieve these ends a number of techniques were incorporated including: electron microscopy, protein purification, sedimentation and image processing. Following expression of FtsZ and subsequent purification, experiments aimed at assessing the activity were conducted. These included determining whether the protein was an active GTPase and capable of self-assembly as the bacterial FtsZ homolog displayed these characteristics. The recombinant protein displayed both of these activities and this result allowed for further characterization. The co-assembly critical concentration and assembly efficiency were determined by sedimentation and were 82.75 μg/ml and 33.4 ± 0.9%, respectively. Bacterial FtsZ assemblies have been reported to be in dynamic exchange with a soluble pool of FtsZ and the existence of a similar pool in plants has been discussed in the literature. Chapter III of this work investigates the composition of the soluble pool in Arabidopsis chloroplasts. Gel chromatography revealed that prior to FtsZ assembly initiation the pool consists solely of dimers. Image processing and native PAGE results suggest that at least one assembly intermediate exists between the dimer and mature filamentous assemblies. The most common intermediate observed in assembly reactions is a tetramer. Three-dimensional renderings of the dimer and tetramer are presented in chapter III and suggest that these oligomeric forms may represent consecutive steps in the assembly mechanism of Arabidopsis FtsZ.

<p>The tubulin homolog FtsZ provides the cytoskeletal framework for bacterial cell division. FtsZ is an essential protein for bacterial cell division, and is the only protein necessary for Z-ring assembly and constriction force generation in liposomes in vitro. The work presented here utilizes structural and genomic analysis methods to investigate FtsZ function for cell division with three separate questions: (1) What is the function of the C-terminal linker peptide in FtsZ? (2) Are there interacting proteins other than those of the divisome that facilitate FtsZ function? (3) Do lateral contact sites exist between protofilaments in the Z ring, resulting in an organized Z-ring substructure?</p><p>The FtsZ protein has an ~50 aa linker between the protofilament-forming globular domain and the C-terminal (Ct) membrane-tethering peptide. This Ct linker is widely divergent across bacterial species, and has been thought to be an intrinsically disordered peptide (IDP). We have made chimeras where we have swapped the <italic>Escherichia coli</italic> IDP for Ct linkers from other bacteria, and even for an unrelated IDP from human &alpha-adducin. Most of these substitutions allowed for normal cell division, suggesting that sequence of the IDP did not matter -any IDP appears to work (with some exceptions). Length, however, was important: IDPs shorter than 39 or longer than 89 aa's had compromised function. We conclude that the Ct linker of FtsZ functions as a flexible tether between the globular domain of FtsZ in the protofilament, and its attachment to FtsA and ZipA at the membrane. As a worm-like-chain, the Ct linker will function as a stiff entropic spring linking the constricting protofilaments to the membrane. </p><p>Previous work from our laboratory found that mutant and foreign FtsZ that do not normally function for cell division can function upon acquisition of a second site suppressor mutation, somewhere in the <italic>E. coli</italic> genome. We expect that some mutant or foreign FtsZ are partially functional for division in <italic>E. coli</italic>. As such, these FtsZ require another mutation that further enables their function. These suppressing mutations may reveal proteins interacting with FtsZ and the divisome, that have previously been unknown. In the present study, we have identified, via whole genome re-sequencing, single nucleotide polymorphisms that allow 11 different foreign and mutant FtsZ proteins to function for cell division. While we see a trend toward mutations in genes related to general metabolism functions in the cell, we have also identified mutations in two genes, <italic>ispA</italic> and <italic>nlpI</italic>, that may be interacting more directly with the cell division mechanism.</p><p>Finally, we have devised a screen to identify mutations in FtsZ that may be involved in lateral bonding between protofilaments. There are presently two proposed models of FtsZ substructure: the scattered or the ribbon model. A major difference between these models is that the scattered model proposed no interaction between adjacent protofilaments in the Z ring, while the ribbon model suggests that adjacent protofilaments are bonded laterally to create an organized substructure of aligned protofilaments. Our screen was designed to identify complementary surface-exposed residues that may be involved in lateral bonding. We initially identified two lateral contact candidate residues: R174, and E250 and mutated them to abrogate FtsZ function. We also mutated L272, which is known to make contacts across the protofilament interface, to look for compensating mutations in these contact residues. Using the screen, we identified a number of secondary mutations in FtsZ that can complement these initial loss-of-function mutations. While this screen has not yielded strong candidates for lateral bonding partners, it has emerged as a high-throughput method for screening large libraries of mutant FtsZ proteins in order to identify compensating mutation pairs.</p> / Dissertation

The objective of this work is to investigate the structures of two nucleotide binding proteins: mevalonate kinase (MVK) and FtsZ. MVK is the key enzyme involved in terpenoid biosynthesis. In this study, we solved the crystal structures of the M. jannaschii MVK apoprotein, as well as the protein in complex with ligands. Its fold was analyzed and firmly established within the GHMP kinase family, in which homoserine kinase (HSK), phosphomevalonate kinase and galactokinase also belong. Structural analysis in combination with enzyme kinetics studies revealed the mechanism of this enzyme upon substrate binding, catalysis and inhibition. In particular, the phosphate-binding loop was found to be critically involved in the binding of nucleotides and terpenoids, via the interaction with a di-phosphate moiety from the ligand. An enzymatic reaction mechanism was constructed based on our structural data and it is consistent with kinetics studies from the literature. In this mechanism, the invariant residue Asp 155 functions as a general base that increases the nucleophilicity of the phosphoryl acceptor. Finally, a virtual screening study has been performed to explore the ligand binding potential of MVK. Compounds predicted to bind MVK were tested and analyzed. FtsZ is a prokaryotic homologue of tubulin that forms the apparatus for bacterial cell division. The structure of a crystal filament of the M. tuberculosis FtsZ complexed with GDP was described in this study. It shows an anti-parallel, left-handed double helical architecture. Compared with the straight crystal filament revealed earlier by other groups, the catalytic T7 loop in our structure is found to be outside the nucleotide binding site, indicating the GTPase is inactive. Furthermore, the buried surface area in our crystal filament is less, probably suggesting the helical FtsZ filament is less stable. We therefore proposed that the hydrolysis of GTP and the releasing of the γ-phosphate group will trigger the rearrangement of the FtsZ fibler, characterized by the exclusion of the T7 loop, which might lead to a less stable helical filament and would be the first step for the disassembly of FtsZ polymer.

No description available.

Thèse (M.Sc.)--Université Laval, 2001. / Bibliogr.: f. 67-74. Publié aussi en version électronique.

Chez les procaryotes, FtsZ est reconnu comme étant la protéine clé impliquée dans le contrôle de la septation lors de la division cellulaire. Le gène correspondant, ftsZ, semblait être hautement conservé dans l’évolution chez les bactéries à Gram positif et à Gram négatif. Afin d'amplifier une région génique homologue chez Pseudomonas aeruginosa, deux amorces dirigées contre une région conservée du gène ftsZ ont été conçues à partir de la table d’utilisation des codons riches en GC. Un amplicon de 220 pb a été généré, séquencé et utilisé comme sonde moléculaire afin de cribler une banque génomique de P. aeruginosa PAO dans le vecteur phagique λSE6. Le phage recombinant isolé et cartographié contenait un fragment d’ADN chromosomique de P. aeruginosa de 16.5 kb. L’analyse de la séquence partielle d’un fragment de 4,5 kb BamHl a révélé un arrangement génique ftsA-ftsZ-envA suggérant une organisation similaire à celle observée chez Escherichia coli. L’étude de l’expression protéique in vitro a démontré la présence d’une protéine de 40 kDa. L’alignement des séquences de 8 gènes ftsZ a démontré que ces protéines sont hautement conservées. Une analyse phylogénétique des gènes ftsZ séparant les espèces en deux groupes de bactéries à Gram positif et à Gram négatif semble en accord avec la phylogénie des ARNr de ces espèces. / Québec Université Laval, Bibliothèque 2018 / Ottawa Bibliothèque nationale du Canada, Direction des acquisitions et des services bibliographiques 19 . --