Anthrax lethal factor (LF) mediated block of the anthrax protective antigen (PA) ion channel: effect of ionic strength and voltage.

The anthrax toxin complex consists of three different molecules, protective antigen (PA), lethal factor (LF), and edema factor (EF). The activated form of PA, PA(63), forms heptamers that insert at low pH in biological membranes forming ion channels and that are necessary to translocate EF and LF in the cell cytosol. LF and EF are intracellular active enzymes that inhibit the host immune system promoting bacterial outgrowth.

Interaction of bacteriophage lambda with its cell surface receptor: an in vitro study of binding of the viral tail protein gpJ to LamB (Maltoporin).

The cell surface receptor for bacteriophage Lambda is LamB (maltoporin). Responsible for phage binding to LamB is the C-terminal part, gpJ, of phage tail protein J. To study the interaction between LamB and gpJ, a chimera protein composed of maltose binding protein (MBP or MalE) connected to the C-terminal part of J (gpJ, amino acids 684-1131) of phage tail protein J of bacteriophage Lambda was expressed in Escherichia coli and purified to homogeneity.

Vegetative insecticidal protein (Vip1Ac) of Bacillus thuringiensis HD201: evidence for oligomer and channel formation.

The binding component (Vip1Ac) of the ADP-ribosylating vegetative insecticidal protein (Vip) of Bacillus thuringiensis HD201 was isolated from the supernatant of cell cultures. Vip1Ac protein solubilized at room temperature ran as oligomers on SDS-PAGE. These oligomers were not resistant to heating.

Site-directed mutagenesis of the greasy slide aromatic residues within the LamB (maltoporin) channel of Escherichia coli: effect on ion and maltopentaose transport.

The 3D-structure of the maltooligosaccharide-specific LamB-channel of Escherichia coli (also called maltoporin) is known from X-ray crystallography. The 3D structure suggests that a number of aromatic residues (Y6, Y41, W74, F229, W358 and W420) within the channel lumen are involved in carbohydrate and ion transport. All aromatic residues were replaced by alanine-scanning mutagenesis.

Anthrax toxin protective antigen: inhibition of channel function by chloroquine and related compounds and study of binding kinetics using the current noise analysis.

Protective antigen (PA) of the tripartite anthrax toxin binds to a cell surface receptor and mediates the transport of two enzymatic components, edema factor and lethal factor, into the cytosol of host cells. Here recombinant PA(63) from Bacillus anthracis was reconstituted into artificial lipid bilayer membranes and formed ion permeable channels. The heptameric PA(63)-channel contains a binding site for 4-aminoquinolones, which block ion transport through PA in vitro.

Mechanism of C2-toxin inhibition by fluphenazine and related compounds: investigation of their binding kinetics to the C2II-channel using the current noise analysis.

The binding component C2II of the binary actin ADP-ribosylating C2-toxin from Clostridium botulinum is essential for intoxication of target cells. Activation by a protease leads to channel formation and this is presumably required for the transport of the toxic C2I component into cells. The C2II-channel is cation selective and contains a binding site for fluphenazine and structurally related compounds.

CymA of Klebsiella oxytoca outer membrane: binding of cyclodextrins and study of the current noise of the open channel.

CymA, the outer membrane component of the cyclodextrin (CD) uptake and metabolism system of Klebsiella oxytoca, was reconstituted into lipid bilayer membranes. The channel properties of this unusual porin were studied in detail. The binding of CDs to the channel resulted in its complete block for ion transport.

Site-directed mutagenesis of tyrosine 118 within the central constriction site of the LamB (maltoporin) channel of Escherichia coli. II. Effect on maltose and maltooligosaccharide binding kinetics.

The 3-D structure of the maltooligosaccharide-specific LamB channel of Escherichia coli (also called maltoporin) is known from x-ray crystallography. The central constriction of the channel formed by the external loop 3 is controlled by tyrosine 118. Y118 was replaced by site-directed mutagenesis by 10 other amino acids (alanine (A), isoleucine (I), asparagine (N), serine (S), cysteine (C), aspartic acid (D), arginine (R), histidine (H), phenylalanine (F), and tryptophan (W)) including neutral ones, negatively and positively charged amino acids to study the effect of their size, their hydrophobicity index, and their charge on maltose and maltooligosaccharide binding to LamB.

Site-directed mutagenesis of tyrosine 118 within the central constriction site of the LamB (Maltoporin) channel of Escherichia coli. I. Effect on ion transport.

The three-dimensional structure of the malto-oligosaccharide-specific LamB-channel of Escherichia coli (also called maltoporin) is known from x-ray crystallography. The central constriction of the channel formed by the external loop 3 is controlled by a tyrosine residue (Y118). Y118 was replaced by site-directed mutagenesis by ten other amino acids (alanine, isoleucine, asparagine, serine, cysteine, aspartic acid, arginine, histidine, phenylalanine, and tryptophane) including neutral ones, negatively and positively charged amino acids to study the effect of their size, hydrophobicity, and charge on ion transport through LamB.