The synthesis and function of the Escherichia coli hemolysin and related RTX exotoxins

Welch, R

doi:10.1016/0378-1097(92)90072-v

Cited by 42 publications

(46 citation statements)

References 35 publications

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“…This outer membrane protein and the similar HpmB outer membrane protein of Proteus mirabilis (55,57) have been shown to be essential for the activation and secretion of the S. marcescens ShlA and P. mirabilis HpmA hemolysins, respectively (4,46,55,57). In contrast to the well-studied RTX cytotoxins (57,58), both of these hemolysins have leader peptides (4,46), as does HxuA (7). In addition, both the Hib and NTHI HxuA proteins possess the amino acid sequence motif A-N-P-N (7) which has been shown to be critical for the activation and secretion of the ShlA hemolysin (4,47).…”

Section: Discussionmentioning

confidence: 99%

A gene cluster involved in the utilization of both free heme and heme:hemopexin by Haemophilus influenzae type b

et al. 1995

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The utilization of heme bound to the serum glycoprotein hemopexin by Haemophilus influenzae type b (Hib) strain DL42 requires the presence of the 100-kDa heme:hemopexin-binding protein encoded by the hxuA gene (M. S. Hanson, S. E. Pelzel, J. Latimer, U. Muller-Eberhard, and E. J. Hansen, Proc. Natl. Acad. Sci. USA 89:1973-1977, 1992). Nucleotide sequence analysis of a 5-kb region immediately upstream from the hxuA gene revealed the presence of two genes, designated hxuC and hxuB, which encoded outer membrane proteins. The 78-kDa HxuC protein had similarity to TonB-dependent outer membrane proteins of other organisms, whereas the 60-kDa HxuB molecule most closely resembled the ShlB protein of Serratia marcescens. A set of three isogenic Hib mutants with cat cartridges inserted individually into their hxuA, hxuB, and hxuC genes was constructed. None of these mutants could utilize heme:hemopexin. The hxuC mutant was also unable to utilize low levels of free heme, whereas both the hxuA and hxuB mutants could utilize free heme. When the wild-type hxuC gene was present in trans, the hxuC mutant regained its ability to utilize low levels of free heme but still could not utilize heme:hemopexin. The hxuA mutant could utilize heme:hemopexin when a functional hxuA gene from a nontypeable H. influenzae strain was present in trans. Complementation analysis using this cloned nontypeable H. influenzae hxuA gene also indicated that the HxuB protein likely functions in the release of soluble HxuA from the Hib cell. These studies indicate that at least two and possibly three gene products are required for utilization of heme bound to hemopexin by Hib strain DL42.

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Section: Discussionmentioning

confidence: 99%

A gene cluster involved in the utilization of both free heme and heme:hemopexin by Haemophilus influenzae type b

et al. 1995

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“…E. coli ␣-hemolysin (HlyA) produces large, clear zones of hemolysis around colonies on blood agar. The hemolysin is present in cell-free filtrates and is the best characterized member of the RTX (repeat in toxin) toxin family (25). HlyA lyses cells by the creation of pores in the target cell membrane and affects erythrocytes, leukocytes (4,5), and renal tubular cells (12).…”

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Occurrence of hlyA and sheA Genes in Extraintestinal Escherichia coli Strains

Kerényi¹,

Allison

Bátai

et al. 2005

J Clin Microbiol

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The association of a hemolytic phenotype with the carriage of the ␣-hemolysin gene (hlyA) and/or the silent hemolysin gene (sheA or clyA) among 540 extraintestinal clinical isolates of Escherichia coli and 110 fecal isolates from healthy individuals was investigated. Though HlyA is an important virulence factor in extraintestinal E. coli infection, the role of SheA is not completely clarified. Two hemolytic sheA ؉ E. coli strains that lacked hlyA and possessed no other hemolysin genes were identified. No hlyA ؉ sheA ؉ strains were identified, suggesting that there is possible incompatibility between hlyA and sheA in the chromosome of E. coli.

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“…Up to now, however, there has been no experimental evidence for expression of an RTX-like toxin or cytolysin in Salmonella, although cytotoxic activity associated with a cholera toxin (CT)-like toxin and an Escherichia coli heat-labile enterotoxin (LT-I)-like toxin has been reported (7,31). Members of the RTX toxin family, and especially the HlyA hemolysin of uropathogenic E. coli, are among the most thoroughly studied cytolytic toxins of gram-negative bacteria (3,48,49). Using a model for experimental infections in mice, it has been established that HlyA is directly involved in the pathogenesis of E. coli infection (14).…”

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Characterization of a Pore-Forming Cytotoxin Expressed by Salmonella enterica Serovars Typhi and Paratyphi A

Oscarsson¹,

Westermark²,

Löfdahl

et al. 2002

Infect Immun

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Cytolysin A (ClyA) is a pore-forming cytotoxic protein encoded by the clyA gene that has been characterized so far only in Escherichia coli. Using DNA sequence analysis and PCR, we established that clyA is conserved in the human-specific typhoid Salmonella enterica serovars Typhi and Paratyphi A and that the entire clyA gene locus is absent in many other S. enterica serovars, including Typhimurium. The gene products, designated ClyA STy and ClyA SPa , show >90% amino acid identity to E. coli cytolysin A, ClyA EC , and they are immunogenically related. The Salmonella proteins showed a pore-forming activity and are hence functional homologues to ClyA EC . The chromosomal clyA STy gene locus was expressed at detectable levels in the serovar Typhi strains S2369/96 and S1112/97. Furthermore, in the serovar Typhi vaccine strain Ty21a, expression of clyA STy reached phenotypic levels, as detected on blood agar plates.

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The synthesis and function of the Escherichia coli hemolysin and related RTX exotoxins

Cited by 42 publications

References 35 publications

A gene cluster involved in the utilization of both free heme and heme:hemopexin by Haemophilus influenzae type b

A gene cluster involved in the utilization of both free heme and heme:hemopexin by Haemophilus influenzae type b

Occurrence of hlyA and sheA Genes in Extraintestinal Escherichia coli Strains

Characterization of a Pore-Forming Cytotoxin Expressed by Salmonella enterica Serovars Typhi and Paratyphi A

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