The atomic structure of the phage Tuc2009 baseplate tripod suggests that host recognition involves two different carbohydrate binding modules

The Gram-positive bacterium Lactococcus lactis, used for the production of cheeses and other fermented dairy products, falls victim frequently to fortuitous infection by tailed phages. The accompanying risk of dairy fermentation failures in industrial facilities has prompted in-depth investigations of these phages. Lactococcal phage Tuc2009 possesses extensive genomic homology to phage TP901-1. However, striking differences in the baseplate-encoding genes stimulated our interest in solving the structure of this host’s adhesion device. We report here the X-ray structures of phage Tuc2009 receptor binding protein (RBP) and of a “tripod” assembly of three baseplate components, BppU, BppA, and BppL (the RBP). These structures made it possible to generate a realistic atomic model of the complete Tuc2009 baseplate that consists of an 84-protein complex: 18 BppU, 12 BppA, and 54 BppL proteins. The RBP head domain possesses a different fold than those of phages p2, TP901-1, and 1358, while the so-called “stem” and “neck” domains share structural features with their equivalents in phage TP901-1. The BppA module interacts strongly with the BppU N-terminal domain. Unlike other characterized lactococcal phages, Tuc2009 baseplate harbors two different carbohydrate recognition sites: one in the bona fide RBP head domain and the other in BppA. These findings represent a major step forward in deciphering the molecular mechanism by which Tuc2009 recognizes its saccharidic receptor(s) on its host

Type IX secretion system PorM and gliding machinery GldM form extended arches spanning the periplasmic space

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Contribution à l'étude de la région "réplication-incompatibilité" du plasmide F

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Application of the cell method to the statistical thermodynamics of solutions. II. Experimental

In connection with the theory of solutions proposed by Prigogine and Mathot [J. Chem. Phys. 20, 49 (1952)], total vapor pressures and volume changes on mixing have been measured for the systems: CCl4-C(Me)4 I C6H12-C(Me)4 II C6H 6-C(Me)4 III. Volume changes only for the systems: CCl(Me)3-CCl4 IV CCl2(Me)2-CCl 4 V CCl3(Me)-CCl4 VI C(Me)3OH- CCl4 VII. For the first three systems I, II, and III, one observes a positive excess free energy (positive deviations to the Raoult law) together with a negative excess volume (contraction on mixing), whereas for the last four IV, V, VI, and VII there is a gradual passage from negative (IV) to positive (VII) excess volume. These results are discussed in terms of the molecular interactions AA, BB, and AB. Reasonable agreement is observed between Prigogine and Mathot's theory and experiment.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Thermodynamics and spectroscopic properties of associated solutions. Part II

Considering an associated binary solution, e.g. alcohol + carbon tetrachloride, as a system of single molecules and associated complexes in equilibrium with one another, it has been shown in a previous paper, by using the principle of detailed balancing of elementary processes, that the relation fA/fB = α holds between the activity coefficients if the deviations from the laws of perfect solutions can be entirely ascribed to the presence of the complexes, α denotes the fraction of molecules of the associated constituent which appear as single molecules. This relation, which is completely independent of any hypothesis about the mode of association, can be checked by comparing thermodynamic measurements of fA and f B with values of α obtained from the spectroscopic study of the intensity of the OH vibration band. We have measured the partial vapour pressures of the system: tert.-butyl alcohol + carbon tetrachloride, tert.-butvl alcohol + cyclohexane, tert.-butyl alcohol + carbon disulphide, for which the spectroscopic values of α are known. In all three cases, as in those studied in our previous work, the relation fA/fB = α holds quite well, except for high concentrations of alcohol. The Gibbs excess free energy has been calculated for the systems mentioned above and for the system methanol + carbon tetrachloride. From the comparison of the thermodynamic data for fA/fB and the spectroscopic data for α it is possible to make a rather accurate estimation of the part of the excess free energy which must be attributed to the presence of the complexes.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Propriétés thermodynamiques des solutions associées

Considering an associated solution, e. g. alcohol‐carbon tetrachloride, as a system of monomolecules and associated complexes in equilibrium with one another, it is shown that the thermodynamic properties, particularly activity coefficients, are completely determined by the chemical potentials of the monomolecules only. Using the principle of detailed balancing of elementary processes, it is shown that the following relation holds between the activity coefficients ƒA/ƒB = α where α is the fraction of molecules of the associated constituent which appear as monomolecules. This relation may be checked by comparing thermodynamic measurements of ƒA, and ƒB with values of a obtained from the spectroscopic study of the intensity of the OH monomolecular vibration band. Different statistical models are used for the calculation of the thermodynamic properties of the associated solutions. The results are compared and discussed. The influence of the size and shape of the associated complexes is studied. The calculated results are compared to the experimental ones for the systems (Formula Presented.) In these three cases, the relation ƒA/ƒB = α holds quite fairly. A direct proof is thus given that the deviations from ideality may be justified by the formation of complexes in these systems. In addition, the comparison of the observed activity coefficients and those calculated by the different statistical models used shows that, in concentrated solutions, an important part of the complexes must be formed by two or three dimensional molecular aggregates. A chain‐association alone is not sufficient to interpret the departures from ideality. Copyright © 1949 Wiley‐VCH Verlag GmbH & Co. KGaA, WeinheimSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Camelid nanobodies: killing two birds with one stone

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Construction in vitro of Phage-plasmid chimerae: a new tool to analyse the mechanism of plasmid maintenance

In this paper, we report the construction in vitro of chimerae between lambdoid replacement vectors (Murray et al. 1977) and the miniF Apr plasmid: pSC138 (Timmis et al. 1975). λF recombinants were shown to be chimerae between the λ and the F replicons. By genetical tests, we have demonstrated that both λ and F replication mechanisms are functional: the λF recombinant behaves as a non defective plaque forming phage on λ sensitive bacteria and establishes itself as a stable plasmid on recA F- homoimmune bacteria. In the extra-chromosomal state, the λF recombinant apparently retains the controlled autonomous replication and the FI incompatibility characteristics of the F plasmid. The potential experimental uses of these phages are discussed. © 1979 Springer-Verlag.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

The F plasmid replication incompatibility region: III. Identification of the proteins involved in the control of the F plasmid maintenance

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The F-plasmid "replication incompatibility" region: II. Mutations affecting the F replication and/or the FI incompatibility

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