The hemolytic effect of Salmonella typhi T y 2 porins
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Two outer membrane proteins of Salmonella typhi T y 2 were extensively co-purified. According to their migration in dodecyl sulfate/polyacrylamide gel electrophoresis and solubility characteristics, these proteins are homologous to the 35-kDA and 36-kDA porins found in Salmonella Typhimurium. A porin homologous to the 34-kDA one has not been found in S. typhi T y 2. A critical step in the purification of porins is haeting at 100ºC in 2% sodium dodecyl sulfate before Sephadex gel filtration. The absence of detergent in aqueous suspensions enhances porin agregation, this aggregations inducing human red cell lysis. Porins obtained by an alternative procedure consisting of heating at 60ªC instead of 100ºC were also hemolytic. Using a nanomolar concentration of porins a strong influence of temperature on the hemolytic effect was observed. Porin-induced hemolysis was inhibited with anti-porin serum, as well as by a treatment with phenylglyoxal, which reacts with the arginine residues of proteins. The membrane-disrupting ability of porins aggregates might explain some pathogenic characteristics of gram-negative bacterial infections.