Twelve monoclonal antibodies (MAbs) produced against the Escherichia coli hemolysin (HlyA) encoded by the hemolysin recombinant plasmid pWAM04 were studied. HlyA derivatives from recombinant strains with different plasmids encoding HlyA amino-terminal and carboxy-terminal truncates, HlyA in-frame deletions, and HlyA frameshift mutations were used in immunoblots to localize the antigenic determi...

Vibrio cholerae produces a cytolytic toxin named El Tor cytolysin/hemolysin which is encoded by the hlyA gene. This cytolysin is produced as a 79-kDa precursor form (pro-HlyA) into the culture supernatant after cleavage of the signal peptide of the hlyA product (prepro-HlyA). The pro-HlyA is then processed to a 65-kDa mature cytolysin (mature HlyA) after cleavage of the 15-kDa N-terminal peptid...

Extra- and intracellular Escherichia coli hemolysin expressed by two cloned hly determinants, both under the control of the activator element hlyR, were analyzed. One determinant carried all four hly genes (hlyC, hlyA, hlyB, and hlyD), whereas the other carried only the two genes (hlyC and hlyA) required for synthesis of active hemolysin but not those essential for its secretion. It was shown t...

Escherichia coli hemolysin (HlyA) is the prototype toxin of a major family of exoproteins produced by Gram-negative bacteria known as "repeats in toxins." Only fatty acid-acylated HlyA molecules at residues Lys564 and Lys690 are able to damage the target cell membrane. Fatty acylation of pro-HlyA is dependent on the co-synthesized acyltransferase HlyC and the acylated form of acyl-carrier prote...

DNA sequence analysis of the regions adjacent to the hlyA gene, which encodes listeriolysin O, an essential virulence factor of Listeria monocytogenes, revealed the presence of two open reading frames (ORFs): ORF D located 304 base pairs downstream from hlyA, and ORF U located 224 base pairs upstream from and in opposite direction to hlyA. Promoter mapping performed with RNAs extracted from cel...

Zinc homoeostasis exerts protective effects in inflammatory intestinal diseases and zinc supplementation has been successfully used for treating infectious diarrhoea. This study aimed at a characterisation of zinc effects on focal leak induction by α-haemolysin (HlyA)-producing Escherichia coli (E. coli) as protective mechanism for colitis. We conducted in vivo experiments by oral challenge of ...

The pore-forming exotoxin α-hemolysin from E. coli causes a significant volume reduction of human erythrocytes that precedes the ultimate swelling and lysis. This shrinkage results from activation of Ca2+-sensitive K+ (KCa3.1) and Cl- channels (TMEM16A) and reduced functions of either of these channels potentiate the HlyA-induced hemolysis. This means that Ca2+-dependent activation of KCa3.1 an...

Flow cytometry was developed as a method to assess the conformation of erythrocyte-bound Escherichia coli hemolysin polypeptide (HlyA). Topology of membrane-associated hemolysin (HlyA(E)) was investigated by testing surface accessibility of HlyA regions in lytic and nonlytic bound states, using a panel of 12 anti-HlyA monoclonal antibodies (MAbs). Hemolysin associates nonlytically with erythroc...

This study describes the presence of 10 hemolysin orthologs in the genome of the opportunistic human anaerobic pathogen Bacteroides fragilis, which is currently classified as a nonhemolytic bacterium. The hemolysins were designated HlyA through HlyI plus HlyIII. All cloned hemolysin genes were able to confer hemolytic activity to a nonhemolytic Escherichia coli strain on blood agar plates. Inte...

Vibrio cholerae non-O1/non-O139 is capable of producing sporadic outbreaks of cholera-like diarrhea; however, the pathogenic mechanisms of this bacterium remain unclear. The objectives of this study were to: 1) compare the apoptosis induction and cytotoxicity between hlyA-positive and hlyA-negative strains of V. cholerae non-O1/non-O139; 2) clarify the molecular mechanisms by which these strain...