Low thermodynamic but high kinetic stability of an antifreeze protein from Rhagium mordax

Dennis Steven Friis, Johannes Lørup Johnsen, Erlend Kristiansen, Peter Westh, Hans Ramløv

    Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

    Abstract

    The equilibrium heat stability and the kinetic heat tolerance of a recombinant antifreeze protein (AFP) from the beetle Rhagium mordax (RmAFP1) are studied through differential scanning calorimetry and circular dichroism spectroscopy. In contrast to other insect AFPs studied with this respect, the RmAFP1 has only one disulfide bridge. The melting temperature, Tm, of the protein is determined to be 28.5°C (pH 7.4), which is much lower than most of those reported for AFPs or globular proteins in general. Despite its low melting temperature, both biophysical and activity measurements show that the protein almost completely refolds into the native state after repeated exposure of 70°C. RmAFP1 thus appears to be kinetically stable even far above its melting temperature. Thermodynamically, the insect AFPs seem to be dividable in three groups, relating to their content of disulfide bridges and widths of the ice binding motifs; high melting temperature AFPs (high disulfide content, TxT motifs), low melting temperature but high refolding capability AFPs (one disulfide bridge, TxTxTxT motifs) and irreversibly unfolded AFPs at low temperatures (no disulfide bridges, TxTxTxTxT motifs). The property of being able to cope with high temperature exposures may appear peculiar for proteins which strictly have their effect at subzero temperatures. Different aspects of this are discussed.
    OriginalsprogEngelsk
    TidsskriftProtein Science
    Vol/bind23
    Udgave nummer6
    Sider (fra-til)760-768
    Antal sider9
    ISSN0961-8368
    DOI
    StatusUdgivet - jun. 2014

    Emneord

    • Antifreeze protein
    • Rhagium mordax
    • Stability
    • thermodynamic stability

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