Secretion of an Aeromonas hydrophila aerolysin by a mutant strain of Escherichia coli

Nieto, José Marıća

doi:10.1016/0378-1097(87)90085-1

Cited by 8 publications

(10 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have shown that the main effect of the hha mutation on hemolysin expression is to increase the rate of transcription of the hlyCA genes (21), despite of the faster decay of the hlyCA mRNA (3). Interestingly, the hha mutation affected also the expression of other heterologous proteins cloned in E. coli (22). The hha gene codes for an 8.6-kDa protein, the Hha protein (21), which is highly homologous to the YmoA protein of Yersinia enterocolitica (7).…”

mentioning

confidence: 99%

hlyM, a transcriptional silencer downstream of the promoter in the hly operon of Escherichia coli

et al. 1995

View full text Add to dashboard Cite

Transcription of the hly operon of transmissible plasmids in Escherichia coli is subject to a tight regulation which also involves various chromosomal genes, such as hha. We have identified a 200-bp region within the hlyC gene, designated hlyM, which modulates hemolysin expression. The deletion of hlyM increased the activity of hly::galK fusion 20-fold. hlyM does not contain any internal promoter, nor is it capable of acting in trans. Our data suggest that the chromosomal Hha protein interacts with hlyM in order to silence the hly promoter. In addition, hlyR, a positive activator of hemolysin expression, seems to suppress the modulatory effect dictated by the Hha protein on the hlyM region.Synthesis and secretion of hemolysin are determined by the hly operon located either on the chromosome or on conjugative plasmids (10). Transcription of the hly operon produces a major 4-kb hlyCA transcript and a minor 8-kb hlyCABD transcript (31). The two transcripts initiate at the same promoter, located upstream of the hlyC gene (12, 31). The minor transcript is thought to be produced by readthrough, or antitermination, at a Rho-independent transcriptional terminator located between hlyA and hlyB (15). Similar patterns of expression have been reported for the leukotoxins of Pasteurella (27) and Actinobacillus (26) species.In the case of the plasmid hly operons, a 600-bp sequence (hlyR) located 1.5 kb upstream of hlyC is known to increase hemolysin expression (29). The primary mechanism by which hlyR exerts its action has been proposed to be antitermination at the hlyA-hlyB transcriptional terminator (15,16).Hemolysin expression is a rather complex process in which chromosomal genes are involved as well. Three of them, tolC (30), hha (9, 21), and more recently sfrB (1), have been identified. The hha gene was identified during analysis of hemolysin expression in cells harboring the hemolytic recombinant plasmid pANN202-312, which contains the cluster hlyCABD from

show abstract

mentioning

confidence: 99%

hlyM, a transcriptional silencer downstream of the promoter in the hly operon of Escherichia coli

et al. 1995

View full text Add to dashboard Cite

show abstract

“…This was done as described previously (Nieto et al, 1987). Outer-membrane isolation and protein analysis.…”

Section: Methodsmentioning

confidence: 99%

“…Surprisingly, no Apr transductant clones could be obtained. A temperature-resistant derivative of strain Hha-2 was obtained as previously described (Nieto et al, 1987), and P1 cm crl 100 transduction was attempted, but again transduction of the Apr marker of strain Hha-2 could not be achieved. In contrast, transduction of the Kmr marker of strain Hha-3 could easily be accomplished.…”

Section: Genetic Analysis Of the Mutations In Strains Hha-2 And Hha-3mentioning

confidence: 99%

Chromosomal Mutations That Increase the Production of a Plasmid-encoded Haemolysin in Escherichia coli

Godessart

Regué

et al. 1988

Microbiology

View full text Add to dashboard Cite

Transposon mutagenesis was used to isolate two Escherichia coli mutants which express very large amounts of haemolysin when carrying the multicopy plasmid pANN202-312. E. coli strain Hha-2 was isolated by Mud1 mutagenesis, and strain Hha-3 by Tn5 mutagenesis. The transposon insertion was chromosomal in both mutants and could be demonstrated to be unrelated to the haemolytic region of the plasmid. The substantial increase in both extracellular and intracellular haemolysin production was dependent upon plasmid copy number and was drastically reduced when either mutant carried the low-copy-number haemolytic plasmid pHly152. In both mutants, the marked increase in extracellular production was dependent upon the specific haemolysin transport genes, hlyB and hlyD. The lack of either gene function resulted in no external haemolysin production. SDS-PAGE analysis showed no change in the pattern of outer-membrane proteins of the mutants, although changes (differing between the two mutants) were seen in their periplasmic proteins. The mutations of both strains (termed hha-2 and hha-3) were mapped at minute 10.5 of the E. coli chromosome. No relation to any known gene affecting gene regulation in E. coli could be found.

show abstract

“…Cell fractionation was performed as described previously [14]. Proteins were separated on 10-13% polyacrylamide gels [151 in a minigel apparatus (Bio-Rad Laboratories, Richmond, CA, U.S.A.).…”

Section: Ce// Fractionationmentioning

confidence: 99%

Characterization of a chromosomal mutant that blocks hemolysin excretion in Escherichia coli

Muñoa¹

1989

FEMS Microbiology Letters

View full text Add to dashboard Cite

Secretion of an Aeromonas hydrophila aerolysin by a mutant strain of Escherichia coli

Cited by 8 publications

References 5 publications

hlyM, a transcriptional silencer downstream of the promoter in the hly operon of Escherichia coli

hlyM, a transcriptional silencer downstream of the promoter in the hly operon of Escherichia coli

Chromosomal Mutations That Increase the Production of a Plasmid-encoded Haemolysin in Escherichia coli

Characterization of a chromosomal mutant that blocks hemolysin excretion in Escherichia coli

Contact Info

Product

Resources

About