Charge displacements during ATP-hydrolysis and synthesis of the Na+-transporting FoF1-ATPase of Ilyobacter tartaricus. (1/21)

Transient electrical currents generated by the Na(+)-transporting F(o)F(1)-ATPase of Ilyobacter tartaricus were observed in the hydrolytic and synthetic mode of the enzyme. Two techniques were applied: a photochemical ATP concentration jump on a planar lipid membrane and a rapid solution exchange on a solid supported membrane. We have identified an electrogenic reaction in the reaction cycle of the F(o)F(1)-ATPase that is related to the translocation of the cation through the membrane bound F(o) subcomplex of the ATPase. In addition, we have determined rate constants for the process: For ATP hydrolysis this reaction has a rate constant of 15-30 s(-1) if H(+) is transported and 30-60 s(-1) if Na(+) is transported. For ATP synthesis the rate constant is 50-70 s(-1).  (+info)

Bacterial alpha2-macroglobulins: colonization factors acquired by horizontal gene transfer from the metazoan genome? (2/21)

BACKGROUND: Invasive bacteria are known to have captured and adapted eukaryotic host genes. They also readily acquire colonizing genes from other bacteria by horizontal gene transfer. Closely related species such as Helicobacter pylori and Helicobacter hepaticus, which exploit different host tissues, share almost none of their colonization genes. The protease inhibitor alpha2-macroglobulin provides a major metazoan defense against invasive bacteria, trapping attacking proteases required by parasites for successful invasion. RESULTS: Database searches with metazoan alpha2-macroglobulin sequences revealed homologous sequences in bacterial proteomes. The bacterial alpha2-macroglobulin phylogenetic distribution is patchy and violates the vertical descent model. Bacterial alpha2-macroglobulin genes are found in diverse clades, including purple bacteria (proteobacteria), fusobacteria, spirochetes, bacteroidetes, deinococcids, cyanobacteria, planctomycetes and thermotogae. Most bacterial species with bacterial alpha2-macroglobulin genes exploit higher eukaryotes (multicellular plants and animals) as hosts. Both pathogenically invasive and saprophytically colonizing species possess bacterial alpha2-macroglobulins, indicating that bacterial alpha2-macroglobulin is a colonization rather than a virulence factor. CONCLUSIONS: Metazoan alpha2-macroglobulins inhibit proteases of pathogens. The bacterial homologs may function in reverse to block host antimicrobial defenses. Alpha2-macroglobulin was probably acquired one or more times from metazoan hosts and has then spread widely through other colonizing bacterial species by more than 10 independent horizontal gene transfers. yfhM-like bacterial alpha2-macroglobulin genes are often found tightly linked with pbpC, encoding an atypical peptidoglycan transglycosylase, PBP1C, that does not function in vegetative peptidoglycan synthesis. We suggest that YfhM and PBP1C are coupled together as a periplasmic defense and repair system. Bacterial alpha2-macroglobulins might provide useful targets for enhancing vaccine efficacy in combating infections.  (+info)

Torque generation by the Fo motor of the sodium ATPase. (3/21)

Based on recent structural and functional findings, we have constructed a mathematical model for the sodium-driven Fo motor of the F1Fo-ATPase from the anaerobic bacterium Propionigenium modestum. The model reveals the mechanochemical principles underlying the Fo motor's operation, and explains all of the existing experimental data on wild-type and mutant Fo motors. In particular, the model predicts a nonmonotonic dependence of the ATP hydrolysis activity on the sodium concentration, a prediction confirmed by new experiments. To explain experimental observations, the positively charged stator residue (R227) must assume different positions in the ATP synthesis and hydrolysis directions. This work also illustrates how to extract a motor mechanism from dynamical experimental observations in the absence of complete structural information.  (+info)

Peripartum bacteremias due to Leptotrichia amnionii and Sneathia sanguinegens, rare causes of fever during and after delivery. (4/21)

We report three cases of delivery and postpartum bacteremia due to unusual anaerobic bacteria in healthy young women. Leptotrichia amnionii bacteremia occurred during delivery in two mothers and was associated with fetal distress during labor. Conversely, Sneathia sanguinegens bacteremia occurred postpartum, 2 days after delivery, without consequence for the neonate.  (+info)

Structure of the rotor ring of F-Type Na+-ATPase from Ilyobacter tartaricus. (5/21)

In the crystal structure of the membrane-embedded rotor ring of the sodium ion-translocating adenosine 5'-triphosphate (ATP) synthase of Ilyobacter tartaricus at 2.4 angstrom resolution, 11 c subunits are assembled into an hourglass-shaped cylinder with 11-fold symmetry. Sodium ions are bound in a locked conformation close to the outer surface of the cylinder near the middle of the membrane. The structure supports an ion-translocation mechanism in the intact ATP synthase in which the binding site converts from the locked conformation into one that opens toward subunit a as the rotor ring moves through the subunit a/c interface.  (+info)

Structural evidence for a constant c11 ring stoichiometry in the sodium F-ATP synthase. (6/21)

The Na+-dependent F-ATP synthases of Ilyobacter tartaricus and Propionigenium modestum contain membrane-embedded ring-shaped c subunit assemblies with a stoichiometry of 11. Subunit c from either organism was overexpressed in Escherichia coli using a plasmid containing the corresponding gene, extracted from the membrane using detergent and then purified. Subsequent analyses by SDS/PAGE revealed that only a minor portion of the c subunits had assembled into stable rings, while the majority migrated as monomers. The population of rings consisted mainly of c11, but more slowly migrating assemblies were also found, which might reflect other c ring stoichiometries. We show that they consisted of higher aggregates of homogeneous c11 rings and/or assemblies of c11 rings and single c monomers. Atomic force microscopy topographs of c rings reconstituted into lipid bilayers showed that the c ring assemblies had identical diameters and that stoichiometries throughout all rings resolved at high resolution. This finding did not depend on whether the rings were assembled into crystalline or densely packed assemblies. Most of these rings represented completely assembled undecameric complexes. Occasionally, rings lacking a few subunits or hosting additional subunits in their cavity were observed. The latter rings may represent the aggregates between c11 and c1, as observed by SDS/PAGE. Our results are congruent with a stable c11 ring stoichiometry that seems to not be influenced by the expression level of subunit c in the bacteria.  (+info)

Formulation and evaluation of PLA and PLGA in situ implants containing secnidazole and/or doxycycline for treatment of periodontitis. (7/21)

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Psychrilyobacter atlanticus gen. nov., sp. nov., a marine member of the phylum Fusobacteria that produces H2 and degrades nitramine explosives under low temperature conditions. (8/21)

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