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PubMed1975

Cellular streptolysin S-related hemolysins of group A Streptococcus C203S.

Group A streptococci strain C203S, grown in heart infusion broth with 0.3% maltose, produce two cellular hemolysins related to extracellular streptolysin S (SLS). Enzymatic lysis of the streptococci by group C streptococcal phage-associated lysin results in release of low titer, labile hemolysin, which can be stabilized by ribonucleic acid (RNA)-core (RNA preparation from yeast). This labile hemolysin can be detected only after the higher titer cellular streptolysin O is removed by erythrocyte membranes or inactivated by N-ethylmaleimide. The other cellular SLS-related hemolysin is released in a latent state (potential hemolysin) which can be activated to high-titer hemolysin by sonication with RNA-core. The titer of such activated hemolysin depends upon the intensity of sonic energy, duration of sonication, and amount of RNA-core. RNA obtained from the streptococci is far less effective than RNA-core. When the cocci are disrupted by sonication or grinding, potential hemolysin and/or activated form may be released, depending upon the conditions employed. The potential hemolysin material is large and heterogeneous; activation appears to involve, in part, disaggregation or fragmentation. Labile hemolysin, potential hemolysin, and the activated form of potential hemolysin can all be converted to hemolysin having the same hemolytic and physical properties as RNA-core SLS, suggesting that all have the same hemolytic moiety. The presence of glucose in heart infusion broth prevents formation of both potential hemolysin and RNA-core SLS by log-phase cells, whereas addition of glucose to a culture in heart infusion broth with 0.3% maltose stops accumulation of potential hemolysin but does not affect continuation of RNA-core SLS release. These results suggest that potential hemolysin is a cellular precursor to RNA-core SLS.

Adsorption↗
PubMed1994

Pore formation by the Escherichia coli alpha-hemolysin: role for mediator release from human inflammatory cells.

The Escherichia coli alpha-hemolysin represents a potent stimulus for inflammatory mediator release (O2-, beta-glucuronidase release, and leukotriene generation) from human polymorphonuclear granulocytes, for histamine release from a suspension of human lymphocyte/monocyte basophil cells (LMB), and for serotonin release and 12-hydroxyeicosatetraenoic acid generation from human platelets. In contrast, the E. coli alpha-hemolysin leads to a downregulation of cytokine release (interleukin-1 beta [IL-1 beta], IL-6, and tumor necrosis factor alpha) from human LMB. Recently, it became apparent that the E. coli alpha-hemolysin is composed of several functional structures. We analyzed the role of pore formation, pore stability, and calcium-dependent membrane binding for inflammatory mediator release by using washed bacteria as well as culture supernatants of isogenic recombinant E. coli strains expressing no hemolysin (Hly-), the wild-type hemolysin (Hly+), or hemolysin molecules deficient or modulated in defined functions (pore formation, calcium-dependent membrane binding, or pore stability). In human granulocytes and platelets, mutant hemolysin with enhanced pore stability did not lead to a further increase in induction; mutant hemolysin deficient in pore-forming activity or calcium-dependent membrane binding no longer induced leukotriene B4 generation or beta-glucuronidase release compared with the wild-type hemolysin. Similar results were obtained with regard to histamine release from human LMB. The induction of cytokine release from human LMB differed depending on the type of mutant E. coli alpha-hemolysin. The wild-type hemolysin, the mutant hemolysin with enhanced pore-forming activity, and, to a lesser degree, the mutant hemolysin deficient in pore-forming activity decreased cytokine release (IL-1 beta, IL-6, IL-8, and tumor necrosis factor) compared with untreated cells. In contrast, the mutant hemolysin deficient in calcium-dependent membrane binding led to an increase of up to 50% in cytokine release compared with that by unstimulated cells. Our results indicate that simultaneous expression of the pore-forming and calcium-dependent membrane-binding activities of the hemolysin molecule was necessary to obtain the full cellular inflammatory response pattern observed with the wild-type hemolysin.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2005

[Binding Characterizations of Asp-hemolysin to Oxidized Low-Density Lipoprotein].

Oxidized low-density lipoprotein (Ox-LDL) is known to be involved in the generation and progression of atherosclerosis. Ox-LDL has a number of potentially atherogenic effects on vascular cells, including uncontrol uptake by scavenger receptors. Asp-hemolysin, a hemolytic toxin from Aspergillus fumigatus, is a binding protein for Ox-LDL. This study was undertaken to clarify the binding specificity of Asp-hemolysin to Ox-LDL. We examined the binding specificity of Asp-hemolysin to Ox-LDL using several modified lipoproteins and scavenger-receptor ligands. Asp-hemolysin bound to Ox-LDL with shorter LDL oxidation times. However, Asp-hemolysin did not bind to acetylated LDL. The native high-density lipoprotein (n-HDL) and modified HDL (e.g., acetylated HDL, oxidized HDL) also had no Asp-hemolysin binding. Inhibitors of scavenger-receptor binding, including maleylated bovine serum albumin, polyinosinic acid, dextran sulfate, and fucoidin, had no effect on the binding of Ox-LDL to Asp-hemolysin. Surface plasmon-resonance studies revealed that Ox-LDL binds with high affinity (K(D)=0.63 microg/ml) to Asp-hemolysin. Furthermore, we have shown that Ox-LDL strongly inhibits the hemolytic activity of Asp-hemolysin and that the removal of lysophosphatidylcholine (lysoPC) from Ox-LDL abolished the inhibition. We also investigated the interaction between Asp-hemolysin and lysoPC as a typical lipid moiety of Ox-LDL. The binding of Asp-hemolysin to LDL oxidized for different times depended on the lysoPC content in each Ox-LDL. In addition, the inhibition of lysoPC production in Ox-LDL by phenylmethylsulfonyl fluoride (PMSF) pretreatment of LDL resulted in a marked decrease in Asp-hemolysin binding to PMSF-pretreated Ox-LDL. The binding analysis of Asp-hemolysin to lysoPC revealed that Asp-hemolysin binds directly to lysoPC. We conclude that Asp-hemolysin is a specific binding protein with high affinity for Ox-LDL and that its binding specificity is distinct from any receptor for Ox-LDL.

Amino Acid Sequence↗
PubMed1986

Identity of hemolysins produced by Vibrio cholerae non-O1 and V. cholerae O1, biotype El Tor.

Hemolysins purified from non-O1 Vibrio cholerae (non-O1 hemolysin) and a Vibrio cholerae O1, biotype El Tor (El Tor hemolysin) were investigated for their homology. The hemolysins were isolated from the culture supernatant fluids by ammonium sulfate precipitation and gel filtration on Sephadex G-100 columns. The purified hemolysins gave single bands with an identical mobility on conventional polyacrylamide gel disc electrophoresis. The molecular weights of the non-O1 and El Tor hemolysins were estimated to be about 60,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the amino acid compositions of the hemolysins were very similar. The specific activities of the hemolysins were identical, and both hemolysins were neutralized to the same extent with antisera against the homologous and heterologous hemolysins. Ouchterlony double immunodiffusion tests with both hemolysins and antihemolysin serum gave a common (fused) precipitin line. These data indicate that the non-O1 hemolysin is biologically, physicochemically, and immunologically indistinguishable from the El Tor hemolysin.

Amino Acids↗
PubMed2006

[Biological activity of Asp-hemolysin as a regulation factor to atherogenic effect by oxidized low-density lipoprotein].

Oxidatively modified low-density lipoprotein (OxLDL) is present in atherosclerotic lesions and has been proposed to play an important role in atherogenesis. Asp-hemolysin, a hemolytic toxin from Aspergillus fumigatus, is a binding protein for OxLDL. This study was undertaken to clarify the biological activity of OxLDL and the potentially of Asp-hemolysin as a regulation factor to atherogenic effect by OxLDL. We first analyzed the interaction between OxLDL and blood coagulation factors, which are involved in the blood coagulation pathway. OxLDL caused prolongation of activated partial thromboplastin time (APTT) as a parameter of the intrinsic pathway of blood coagulation in a dose- and oxidation time-dependent manner. In addition, OxLDL significantly inhibited blood coagulation factor VIII, IX, and XI activity. Furthermore, we demonstrated that factor VIII binds to OxLDL. These results indicate that the binding of factor VIII to OxLDL affects the intrinsic pathway of the blood coagulation cascade. Next, to clarify the structure-function relationship of Asp-hemolysin, we expressed Asp-hemolysin in Escherichia coli as a fusion protein with a maltose-binding protein (MBP) and purified it by affinity chromatography. The purified recombinant Asp-hemolysin showed an immunoreactivity with the anti-Asp-hemolysin antibody. In addition, MBP-Asp-hemolysin fusion protein exhibited binding activity to Ox-LDL as did native Asp-hemolysin. Furthermore, to investigate the effect of the Asp-hemolysin-related peptide (P-21), a synthetic peptide derived from a region of Asp-hemolysin that is rich in positive charges, on macrophage proliferation induced by OxLDL. P-21 inhibited OxLDL-induced macrophage proliferation in a dose-dependent manner. In addition, the binding analysis of P-21 to OxLDL indicated that P-21 binds to OxLDL. These results indicate that P-21 inhibits the OxLDL-induced macrophage proliferation through binding of P-21 to OxLDL. In conclusion, we have shown that OxLDL affects the intrinsic pathway of blood coagulation, and its mechanism is dependent on the binding of factor VIII to OxLDL. Furthermore, we indicate the possibility that Asp-hemolysin is a useful tool to investigate the pathophysiological significance of OxLDL. In particular, since the P-21, an Asp-hemolysin-related peptide, inhibits the OxLDL-induced macrophage proliferation through binding of P-21 to OxLDL, further study on the binding mechanism between Asp-hemolysin-related peptide and OxLDL may provide important information on the prevention and treatment of atherosclerosis.

Aspergillus fumigatus↗
PubMed1968

Cell to cell interaction in the immune response. II. The source of hemolysin-forming cells in irradiated mice given bone marrow and thymus or thoracic duct lymphocytes.

The number of discrete hemolytic foci and of hemolysin-forming cells arising in the spleens of heavily irradiated mice given sheep erythrocytes and either syngeneic thymus or bone marrow was not significantly greater than that detected in controls given antigen alone. Thoracic duct cells injected with sheep erythrocytes significantly increased the number of hemolytic foci and 10 million cells gave rise to over 1000 hemolysin-forming cells per spleen. A synergistic effect was observed when syngeneic thoracic duct cells were mixed with syngeneic marrow cells: the number of hemolysin-forming cells produced in this case was far greater than could be accounted for by summating the activities of either cell population given alone. The number of hemolytic foci produced by the mixed population was not however greater than that produced by an equivalent number of thoracic duct cells given without bone marrow. Thymus cells given together with syngeneic bone marrow enabled irradiated mice to produce hemolysin-forming cells but were much less effective than the same number of thoracic duct cells. Likewise syngeneic thymus cells were not as effective as thoracic duct cells in enabling thymectomized irradiated bone marrow-protected hosts to produce hemolysin-forming cells in response to sheep erythrocytes. Irradiated recipients of semiallogeneic thoracic duct cells produced hemolysin-forming cells of donor-type as shown by the use of anti-H2 sera. The identity of the hemolysin-forming cells in the spleens of irradiated mice receiving a mixed inoculum of semiallogeneic thoracic duct cells and syngeneic marrow was not determined because no synergistic effect was obtained in these recipients in contrast to the results in the syngeneic situation. Thymectomized irradiated mice protected with bone marrow for a period of 2 wk and injected with semiallogeneic thoracic duct cells together with sheep erythrocytes did however produce a far greater number of hemolysin-forming cells than irradiated mice receiving the same number of thoracic duct cells without bone marrow. Anti-H2 sera revealed that the antibody-forming cells arising in the spleens of these thymectomized irradiated hosts were derived, not from the injected thoracic duct cells, but from bone marrow. It is concluded that thoracic duct lymph contains a mixture of cell types: some are hemolysin-forming cell precursors and others are antigen-reactive cells which can interact with antigen and initiate the differentiation of hemolysin-forming cell precursors to antibody-forming cells. Bone marrow contains only precursors of hemolysin-forming cells and thymus contains only antigen-reactive cells but in a proportion that is far less than in thoracic duct lymph.

Animals↗
PubMed1984

Characterization of Escherichia coli hemolysins conferring quantitative differences in virulence.

Recombinant plasmids encoding hemolysins (hly) isolated from four different Escherichia coli strains were found to be very similar by restriction endonuclease fragment analysis within the hemolysin region. Each of the four recombinant plasmids were used to transform a nonhemolytic fecal strain of E. coli. The comparative virulence of the transformants was tested in a rat model of peritonitis. Despite the physical similarity among the hemolysin recombinant plasmids, each conferred different normally avirulent fecal E. coli strain. Reciprocal exchange of similar restriction endonuclease fragments enabled the construction of hybrid hemolysin determinants with two hemolysins of disparate extracellular hemolysin production and relative virulence levels. The hybrid plasmids were introduced into the standard avirulent fecal strain and tested in the rat peritonitis model. The region conferring quantitative differences in extracellular hemolysin production and virulence was found to be within a region of less than 1 kilobase where the hly c cistron is encoded as well as the probable transcription initiation ares for the entire hemolysin operon. A 750-base pair (bp) AvaI fragment from this region was isolated from a virulent hemolysin recombinant and inserted into a common AvaI site present in an avirulent hemolysin plasmid. This insertion resulted in an increase in the amount of extracellular hemolysin activity and the associated virulence when in the fecal E. coli background.

Animals↗
PubMed1989

Molecular cloning and characterization of a hemolysin gene from Actinobacillus (Haemophilus) pleuropneumoniae.

This article describes the molecular cloning and expression of a hemolysin gene from a serotype 1 strain of Actinobacillus pleuropneumoniae. The hemolysin was a thermolabile protein with an apparent molecular weight of 29,500 (29.5K hemolysin). Unlike expression of the recently described 105K hemolysin of A. pleuropneumoniae (J. Frey and J. Nicolet, FEMS Microbiol. Lett. 55:41-46, 1988), expression of this hemolysin was not regulated by Ca2+. Antiserum prepared against the 105K hemolysin did not neutralize the activity of the 29.5K hemolysin; conversely, antiserum prepared against the 29.5K hemolysin did not neutralize the activity of the 105K hemolysin. The hemolytic activity was not neutralized with antisera against hemolytic Escherichia coli, Streptococcus agalactiae, or purified streptolysin O, but antisera prepared against recombinants containing the 29.5K gene and convalescent pig sera abrogated hemolytic activity. Although hemolytic activity could be detected in several strains of E. coli K-12 and in minicells expressing several different constructs encoding the 29.5K hemolysin, we could not rigorously exclude the possibility that the gene which we have isolated encodes a regulator of hemolytic activity rather than a hemolysin per se.

Actinobacillus↗