Crystal Structure of Exotoxin A from Aeromonas Pathogenic Species

Abstract

Aeromonas exotoxin A (AE) is a bacterial virulence factor recently discovered in a clinical case of necrotising fasciitis caused by the flesh-eating Aeromonas hydrophila. Here, database mining shows that AE is present in the genome of several emerging Aeromonas pathogenic species. The X-ray crystal structure of AE was solved at 2.3 Å and presents all the hallmarks common to diphthamide-specific mono-ADP-ribosylating toxins, suggesting AE is a fourth member of this family alongside the diphtheria toxin, Pseudomonas exotoxin A and cholix. Structural homology indicates AE may use a similar mechanism of cytotoxicity that targets eukaryotic elongation factor 2 and thus inhibition of protein synthesis. The structure of AE also highlights unique features including a metal binding site, and a negatively charged cleft that could play a role in interdomain interactions and may affect toxicity. This study raises new opportunities to engineer alternative toxin-based molecules with pharmaceutical potential.

Cell Death Signaling Pathway Induced by Cholix Toxin, a Cytotoxin and eEF2 ADP-Ribosyltransferase Produced by Vibrio cholerae

“…mART domain had, respectively, 72% and 46% identity with amino acid sequences of PEA and Cholix [43]. As shown in Figure 1, charged amino acid residues on the surfaces of the three mART toxins are different.…”

“…The crystal structure of a new exotoxin from Aeromonas hydrophila resembles those of PEA and Cholix [ 43 ] ( Figure 1 ). The primary amino acid sequence of Aeromonas exotoxin A exhibited, respectively, 64% and 35% identity with PEA and Cholix, while its C-terminal mART domain had, respectively, 72% and 46% identity with amino acid sequences of PEA and Cholix [ 43 ]. As shown in Figure 1 , charged amino acid residues on the surfaces of the three mART toxins are different.…”

“…The structures of the NAD + -binding pockets in the C-terminal domains also vary. While Cholix possesses an ED E TV sequence around the catalytic Glu581 (underlined), PEA and Aeromonas exotoxin A have an RL E TI sequence [ 43 ]. Jørgensen et al reported that the K m(NAD + ) of Cholix is lower than that of PEA [ 22 ].…”

ISOLATION AND PURIFICATION OF ANTICANCER PROTEIN EXOTXIN A FROM Pseudomonas aeruginosa

“…This bacterium was found to be one of the causative agents of bacteria causing bacteremia in the patient's tissue or organ transplant, causing approximately 28% of bacteremia at all (2).A very toxic virulence component produced naturally by P. aeruginosa is exotoxin A (PE), This toxin was first detected by Liu, A strain that is deficient in protease production was considered a good producer of toxin compared with the strain that was actively producing protease (9,29). Exotoxin A is a heat-labile single polypeptide, consisted of 613 amino acid series with a molecular weight of 66 kilodalton (25,18), Exotoxin A which inhibits protein biosynthesis (27). These types of toxin enhance the transference of ADP ribose from NAD+ (nicotinamide adenine dinucleotide) to diphthamide, which leads to suppress the synthesis of protein and consequently lead to eukaryotic cells death (18), which kills the cells through inhibition of protein synthesis, formed by Pseudomonas aeruginosa.…”

“…Exotoxin A is a heat-labile single polypeptide, consisted of 613 amino acid series with a molecular weight of 66 kilodalton (25,18), Exotoxin A which inhibits protein biosynthesis (27). These types of toxin enhance the transference of ADP ribose from NAD+ (nicotinamide adenine dinucleotide) to diphthamide, which leads to suppress the synthesis of protein and consequently lead to eukaryotic cells death (18), which kills the cells through inhibition of protein synthesis, formed by Pseudomonas aeruginosa. The main PE domains elucidated by their crystallographic structure contain the Ia domain (1-252 amino acids), which combines for the receptor of the R2 macroglobulin sited in cells of the animal.…”