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The biochemical properties of the catalytic C-terminal domain of SpvB (C/SpvB) were compared with the enzyme components of C2 toxin and iota toxin. The maximal reaction rates were comparable for all toxins, whereas variable K(sub m) values for NAD were evident.

Research was conducted to examine the possible roles of two conserved tyrosines and two conserved arginines by taking into consideration the influence of chemical modifiers and site-directed mutagenesis. The acyltransferase activity was lowered by the modification of arginine residues with PG. Results demonstrate that four separate mutations of the two conserved arginine residues, under optimum conditions, had negligible effect on acyltransferase activity.

A study was conducted on Escherichia coli subunit toxins called verotoxins (VT) and the molecular basis for the binding of the receptor of the VT1 holotoxin, globotriaosylceramide (Gb3) by the VT1 B-subunit. The experiment demonstrates that a fluorescent derivative of Gb3 possessing a coumarin probe in place of the acyl group normally attached to the Gb3 ceramide moiety is useful for monitoring interactions between VT1B and its receptor.

A study was conducted on the link between the oxidation-reduction properties of the cofactor and its interactions with the apoprotein in different electron transfer proteins. The experiment conducted several amino acid substitutions at positions 57 and 58 in the Clostridium beijerinkii flavodoxin. Results provide direct experimental evidence which strongly support several long standing hypotheses advanced by certain researchers in previous studies.

A study was conducted to analyze the stability of various types of the alpha-toxin from Staphylococcus aureus. Differential scanning calorimetry and limited proteolysis were utilized to carry out the analysis. The thermal unfolding of the alpha-toxin was assumed to be correlated with the post-transitional aggregation of the protein. Results indicated that the membrane-inserted alpha-toxin channel does not support cooperative unfolding. Findings also showed that it is highly susceptible to proteases.

Verotoxins are a class of bacterial toxins whose morphology constitutes an enzymatic A subunit where the toxic activity resides and is linked to a B oligomer that binds to specific cell-surface carbohydrate receptors. The solution structure of this carbohydrate B subunit of verotoxin VT-1 from the enterohemmorrhagic Escherichia coli is determined in relation to the trimethylsilylethyl derivative of the trisaccharide moiety of Gb3. The solution structure was obtained using nuclear magnetic resonance methods and is described.

Research was conducted to study the hypothesis that the movement of a loop in domain 3 of aerolysin is required for channel formation. Experimental results support the concept that the loop in domain 3 of aerolysin must veer away from the beta-sheet before oligomerization can take place. Findings also reveal that the bridge locking the loop to the beta-sheet inactivates the protein at a step following activation.

Research was conducted to study the binding specificity in protein-protein recognition in the colicin DNase-immunity protein system. Focus of the research was on a class of toxins in the E group colicins which have the ability to kill Escherichia coli cells by the action of an endonuclease domain. Results indicate that specificity in the colicin-immunity system is controlled by a dual recognition mechanism wherein stabilizing interactions from the conserved regions of an immunity protein are considered as the binding site anchor.

The low-pH solution properties of crm45, a mutant form of diphtheria toxin that is truncated at Thr386 was characterized using measurements of the sedimentation rate, analytical ultracentrifugation and diffusion coefficient of crm45 at pH 5.0 which resulted in a molecular mass determination of 890 + or - 40 kDa for the oligomer. Results suggest the ph-dependent formation of a uniformly sized, 20-24 subunit oligomer of the C and T domains of DT in solution.

The secondary structure and interaction of the C-terminal 63 kDa of protective antigen (PA63) and edema toxin (EF) with lipid membrane were probed through attenuated total reflection Fourier transform infrared spectroscopy. Results have shown that the membrane interaction was mediated by the formation of the beta-sheets with the presence of intersheets hydrogen bonds. The strong interaction of LF and EF with the lipid membrane in the absence of PA63 indicated their role in translocation by forming a complex with PA63.

The crystal structure of diphtheria toxin (DT) in complex with nicotinamide adenine dinucleotide (NAD) was analyzed to determine how the catalytic (C) domain of DT binds with NAD and catalyzes the adenosine diphosphate-ribosylation of elongation factor-2 (EF-2). Residues 39-46 of the active-site loop of the C-domain became disarranged after NAD binding. The negatively charged phosphates and two ribosyl hydroxyls of NAD presented a surface for interaction with EF-2.

Toxic shock syndrome toxin 1 (TSST-1) from Staphylococcus aureus shows structural homology to a superantigen, staphylocaccal enterotoxin B (SEB). The area encompassing the carbonyl terminal of the central helix is the source of the superantigenicity of SEB and TSST-1. The primary dissimilarity of the two molecules lies in the amino terminuses and the extent to which surface loops cover the central helix.

Aerolysin mutants in which the trytophan at positions 371 or 373 was replaced with leucine was found to have a slightly different tertiary structure and was capable of oligomerizing at much lower concentrations compared to the wild-type bacterial toxin. The L-373 and L-371 mutant toxins were also capable of causing chloride release from liposomes more readily than the wild-type protein, which was found to be incapable of inducing the same effect in the absence of oligomeric toxin. It was concluded that the insertion of oligomers formed in solution is responsible for the formation of aerolysin channels.

A method for purifying ADP-ribosylated proteins was developed. The procedure involved the synthesis of biotinylated nicotinamide adenine dinucleotide (NAD) which was then used as a substrate for ADP-ribosylation. The ADP-ribosylated protein could then be purified by avidin affinity chromatography. The procedure was applied on elongation factor-2 and nitric oxide-stimulated ADP-ribosylated protein in rat brain.

A study is conducted to determine the amino acids within dodecapetide region (toxic shock syndrome toxin-I amino acids F119-D130) from Staphylococcus aureus that are required for interaction with vaginal epithelium. The results suggested that the toxic shock syndrome toxin-1 residue D130 might contribute to binding an epithelial receptor that facilitates it to penetrate the vaginal mucosa, include interleukin-8, and cause toxic shock syndrome

The construction and characterization of a library consisting of 75% of all possible single-site mutants of the 101-residue, homodimeric Escherichia coli toxin CcdB is reported. The results from the analysis of expression and solubility of ts mutants provide insight into molecular determinants of the temperature sensitive (ts) phenotype and the new pathway to design the ts mutants of any globular protein.

The cloning and identification of a cadherin-like protein AgCad1 cDNA from the gut of Anopheles gambiae larvae and its possible role as a receptor for Cry4Ba toxin of Bacillus thuringiensis strain israelensis is described. The result based on binding thermodynaics of CR11-MPED demonstrates that midgut cadherin, AgCad1, is a Cry4Ba binding protein and putative receptor.

The carrier moiety of heat-labile enterotoxin of Escherichia coli (EtxB) is formed by the noncovalent association of identical monomeric subunits. These subunits assemble in vivo and in vitro into exceptionally stable pentameric complexes.

It is possible to obtain up to 80% yields of reassembled pentamer in vitro from material disassembled for very short incubation periods in KC1-HC1, pH 10. The reassembly yield decreases to no more than 20% when the incubation period in acid is extended.

The selection of human growth-regulatory lectin galectin-1 for ganlioside GM1 versus bacterial toxins is done using the NMR spectroscopy and computational methods. The measurements on the lectin-pentasaccharide complex have revealed differential conformer selection regarding the sialylgalactose linkage in the tri-versus pentasaccharide.