Bovine lactoferrin interacts with cable pili of Burkholderia cenocepacia

In this study we evaluated the ability of lactoferrin, the most abundant antimicrobial protein in airway secretions, to bind the surface structures of a Burkholderia strain cystic fibrosis-isolated. Burkholderia cenocepacia is a gram-negative bacterium involved as respiratory pathogen in cystic fibrosis patient infections. This bacterium possesses filamentous structures, named cable pili that have been proposed as virulence factors because of their ability to bind to respiratory epithelia and mucin. Previously, we demonstrated that bovine lactoferrin was able to influence the efficiency of invasion of different iron-regulated morphological forms of B. cenocepacia. Bovine lactoferrin showed to efficiently inhibit invasion of alveolar epithelial cells by free-living bacteria or iron-induced aggregates or biofilm. Results of the present study demonstrate that bovine lactoferrin is also able to specifically bind to B. cenocepacia cells and show that cable pili are involved in this interaction. The attachment of bovine lactoferrin to pili led to a reduced binding of bacterial cells to mucin. Since cable pili are implicated in mediating the bacterial interactions with mucin and epithelial cells, lactoferrin binding to these structures could play an important role in neutralizing bacterial infection in cystic fibrosis patients.     

Voltage-dependent Inwardly Rectifying Potassium Conductance in the Outer Membrane of Neuronal Mitochondria

Potassium fluxes integrate mitochondria into cellular activities, controlling their volume homeostasis and structural integrity in many pathophysiological mechanisms. The outer mitochondrial membrane (OMM) is thought to play a passive role in this process because K⁺ is believed to equilibrate freely between the cytosol and mitochondrial intermembrane space. By patch clamping mitochondria isolated from the central nervous systems of adult mitoCFP transgenic mice, we discovered the existence of I_OMMKi, a novel voltage-dependent inwardly rectifying K⁺ conductance located in the OMM. I_OMMKi is regulated by osmolarity, potentiated by cAMP, and activated at physiological negative potentials, allowing K⁺ to enter the mitochondrial intermembrane space in a controlled regulated fashion. The identification of I_OMMKi in the OMM supports the notion that a membrane potential could exist across this membrane in vivo and suggests that the OMM possesses regulated pathways for K⁺ uptake.     

Molecular biology of amyotrophic lateral sclerosis: insights from genetics

Amyotrophic lateral sclerosis (ALS) is a paralytic disorder caused by motor neuron degeneration. Mutations in more than 50 human genes cause diverse types of motor neuron pathology. Moreover, defects in five Mendelian genes lead to motor neuron disease, with two mutations reproducing the ALS phenotype. Analyses of these genetic effects have generated new insights into the diverse molecular pathways involved in ALS pathogenesis. Here, we present an overview of the mechanisms for motor neuron death and of the role of non-neuronal cells in ALS.     

Selection and identification of a Listeria monocytogenes target strain for pulsed electric field process optimization

Nine Listeria monocytogenes strains were treated individually with a continuous pulsed electric field (PEF) apparatus, and their sensitivities to the treatment were compared at 25 kV/cm. When cell suspensions of these strains in 0.1% NaCl (pH 7.0) were treated at 23 degrees C for 144 micro s, inactivation ranged from 0.7 to 3.7 log(10) CFU/ml. Inactivation by 72- micro s PEF treatments at 37 degrees C ranged from 0.3 to 2.5 log(10) CFU/ml. L. monocytogenes OSY-8578 was substantially more resistant than other strains when cells were PEF treated in 0.1% NaCl, whereas Scott A was one of the most sensitive strains. The superiority of OSY-8578's resistance to that of Scott A was confirmed in 50% diluted acid whey (pH 4.2). Changes in sensitivity to PEF during phases of growth were minimal in OSY-8578 and substantial in Scott A. Use of L. monocytogenes OSY-8578, therefore, is recommended in studies to optimize PEF processes that target L. monocytogenes. The nine L. monocytogenes strains were genotyped with pulsed-field gel electrophoresis (PFGE) and arbitrarily primed PCR (AP-PCR) techniques. These strains were better differentiated with PFGE than with AP-PCR. The target strain (OSY-8578) was characterized by both molecular typing techniques, but resistance to PEF, in general, was not associated with a particular genotype group.     

Habitat-specific diversity of Borrelia burgdorferi sensu lato in Europe,exemplified by data from Latvia

The distribution of Borrelia burgdorferi sensu lato genospecies in questing Ixodes ricinus ticks from ecologically distinct habitats in Latvia was analyzed. A significant variation in the frequency of the genospecies across sites was observed, pointing to the importance of the host community in the ecology of Lyme borreliosis.     

A novel interaction partner for the C-terminus of Arabidopsis thaliana plasma membrane H+-ATPase (AHA1 isoform): site and mechanism of action on H+-ATPase activity differ from those of 14-3-3 proteins

Using the two-hybrid technique we identified a novel protein whose N-terminal 88 amino acids (aa) interact with the C-terminal regulatory domain of the plasma membrane (PM) H+-ATPase from Arabidopsis thaliana (aa 847-949 of isoform AHA1). The corresponding gene has been named Ppi1 for Proton pump interactor 1. The encoded protein is 612 aa long and rich in charged and polar residues, except for the extreme C-terminus, where it presents a hydrophobic stretch of 24 aa. Several genes in the A. thaliana genome and many ESTs from different plant species share significant similarity (50-70% at the aa level over stretches of 200-600 aa) to Ppi1. The PPI1 N-terminus, expressed in bacteria as a fusion protein with either GST or a His-tag, binds the PM H+-ATPase in overlay experiments. The same fusion proteins and the entire coding region fused to GST stimulate H+-ATPase activity. The effect of the His-tagged peptide is synergistic with that of fusicoccin (FC) and of tryptic removal of a C-terminal 10 kDa fragment. The His-tagged peptide binds also the trypsinised H+-ATPase. Altogether these results indicate that PPI1 N-terminus is able to modulate the PM H+-ATPase activity by binding to a site different from the 14-3-3 binding site and is located upstream of the trypsin cleavage site.     

Evidence for an electrogenic ATPase in microsomal vesicles from pea internodes

The transmembrane electropotential of microsomal vesicles from pea internode segments, monitored by equilibrium distribution of the permeant anion SCN^?, is strongly hyperpolarized when ATP is present in the incubation medium.The stimulation of SCN^? uptake by ATP is rather specific with respect to the other nucleoside di- and triphosphates tested: ADP, GTP, CTP and UTP. ATP-stimulated SCN^? uptake is strongly inhibited by ATPase inhibitors such as $\text{p-}\text{chloromercuribenzenesulphonate}$ and $\text{N,N}{}^{\mathrm{\prime }}\text{-}\text{dicyclohexylcarbodiimide}$ and by 2.5% toluene/ethanol (1 : 4, v/v), the latter being a treatment which makes the vesicles permeable. On the contrary, oligomycin is almost ineffective in influencing ATP-induced SCN^? uptake. The proton conductor carbonyl cyanide $\text{p-}\text{trifluoromethoxyphenylhydrazone}$ strongly inhibits ATP-stimulated SCN^? uptake. The effect of ATP on SCN^? uptake depends on the pH of the medium, the maximum being reached at about pH 7.0.These data support the view that microsomal fractions from pea internodes contain membrane vesicles endowed with a membrane-bound ATPase coupling ATP hydrolysis to electrogenic transport of ions, probably H⁺.     

Identification of two outer membrane proteins involved in the oxidation of sulphur compounds in Thiobacillus ferrooxidans

Abstract: Shift of three Thiobacillus ferrooxidans strains from Fe(II) to S⁰ or thiosulphate liquid medium caused distinctive changes in the outer membrane protein profile. In addition to a new 55-kDa protein which was synthesized only in the presence of sulphur compounds, a higher expression of a 47-kDa protein was observed. This latter protein appeared to be constitutively synthesized, since it was detectable in small amounts even in tile presence of ferrous iron as sole energy source, but its expression was greatly enhanced when elemental sulphur or thiosulphate were present in the growth medium.