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Thermodynamic properties of the effector domains of MARTX toxins suggest their unfolding for translocation across the host membrane
Author(s) -
Kudryashova Elena,
Heisler David,
Zywiec Andrew,
Kudryashov Dmitri S.
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12615
Subject(s) - effector , biology , thermolabile , biophysics , cytoplasm , microbiology and biotechnology , biochemistry , enzyme
Summary MARTX (multifunctional autoprocessing repeats‐in‐toxin) family toxins are produced by V ibrio cholerae , V ibrio vulnificus , A eromonas hydrophila and other G ram‐negative bacteria. Effector domains of MARTX toxins cross the cytoplasmic membrane of a host cell through a putative pore formed by the toxin's glycine‐rich repeats. The structure of the pore is unknown and the translocation mechanism of the effector domains is poorly understood. We examined the thermodynamic stability of the effector domains of V . cholerae and A . hydrophila MARTX toxins to elucidate the mechanism of their translocation. We found that all but one domain in each toxin are thermodynamically unstable and several acquire a molten globule state near human physiological temperatures. Fusion of the most stable cysteine protease domain to the adjacent effector domain reduces its thermodynamic stability ∼ 1.4‐fold (from D G H 2 O21.8 to 16.1 kJ mol −1 ). Precipitation of several individual domains due to thermal denaturation is reduced upon their fusion into multi‐domain constructs. We speculate that low thermostability of the MARTX effector domains correlates with that of many other membrane‐penetrating toxins and implies their unfolding for cell entry. This study extends the list of thermolabile bacterial toxins, suggesting that this quality is essential and could be susceptible for selective targeting of pathogenic toxins.