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Asp‐863 is a key residue for calcium‐dependent activity of Escherichia coli RTX toxin α‐haemolysin
Author(s) -
Cortajarena Aitziber L,
Goñi Félix M,
Ostolaza Helena
Publication year - 2003
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(03)00595-7
Subject(s) - lytic cycle , escherichia coli , mutant , hemolysin , residue (chemistry) , toxin , chemistry , biochemistry , biology , virus , virulence , gene , virology
α‐Haemolysin is a protein toxin secreted by pathogenic strains of Escherichia coli and requires sub‐millimolar Ca 2+ for optimum lytic activity. As a member of the so‐called RTX toxin family it contains a Gly‐rich, Asp‐rich Ca 2+ ‐binding domain, consisting of a series of nonapeptides repeated in tandem. Asp‐863 is located immediately after the last‐but‐one nonapeptide. A mutant in which Asp‐863 has been substituted by Gly displays a requirement for Ca 2+ that is 100‐fold higher than the wild‐type. Membrane lytic activity, as well as a conformational change revealed through an increase in intrinsic fluorescence, and the appearance of Ca 2+ ‐bound protein monomers resolvable by fast protein liquid chromatography, are all three dependent on Ca 2+ concentrations in the 2–20 mM range. Most RTX toxins have an Asp or Glu residue located at a position homologous to Asp‐863, thus the key role of this residue for Ca 2+ requirements of α‐haemolysin may be a general feature of this family of toxins.