Remarkable destabilization of recombinant alpha-lactalbumin by an extraneous N-terminal methionyl residue

Authors:
  • TCT. Chiba
    T. Chiba
  • LCL. T. Chen
    L. T. Chen
  • ASA. Shimizu
    A. Shimizu
  • MIM. Ikeguchi
    M. Ikeguchi
  • SSS. Sugai
    S. Sugai
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Abstract
A recombinant bovine alpha-lactalbumin, possessing an additional N-terminal methionyl residue, was expressed in Escherichia coli. In order to address the effects of the N-terminal methionyl residue on conformational stability, the thermal stability of the recombinant alpha-lactalbumin was investigated by measuring temperature-dependence of circular dichroism spectra, and it was compared with that of authentic alpha-lactalbumin from bovine milk. The thermal stability of the recombinant alpha-lactalbumin was significantly lower than that of authentic alpha-lactalbumin. The enthalpy change of unfolding of the recombinant protein was found to be the same as that of the authentic one when compared at the same temperature. Therefore, the N-terminal methionyl residue seems to destabilize the conformation of recombinant alpha-lactalbumin through some entropic effects.
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