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A stability transition at mildly acidic pH in the alpha‐hemolysin (alpha‐toxin) from Staphylococcus aureus
Author(s) -
Bortoleto Raquel Kely,
Ward Richard J
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01246-6
Subject(s) - chemistry , hemolysin , urea , staphylococcus aureus , denaturation (fissile materials) , tryptophan , elution , circular dichroism , alpha (finance) , chromatography , nuclear chemistry , biophysics , biochemistry , amino acid , bacteria , biology , patient satisfaction , medicine , genetics , construct validity , nursing , virulence , gene
The effects of mildly acidic conditions on the free energy of unfolding (Δ G u buff ) of the pore‐forming alpha‐hemolysin (αHL) from Staphylococcus aureus were assessed between pH 5.0 and 7.5 by measuring intrinsic tryptophan fluorescence, circular dichroism and elution time in size exclusion chromatography during urea denaturation. Decreasing the pH from 7.0 to 5.0 reduced the calculated Δ G u buff from 8.9 to 4.2 kcal mol −1 , which correlates with an increased rate of pore formation previously observed over the same pH range. It is proposed that the lowered surface pH of biological membranes reduces the stability of αHL thereby modulating the rate of pore formation.