Thermomyces Lanuginosus Xylanase Unfolds to a Structure with Large Random Coi Content Below 24 $#730;C AT pH 7.0

Thermomyces lanuginosus xylanase is a thermophilic enzyme with maximum activity at 55 °C. Previous work in our laboratory has determined that it undergoes a large conformational change at 24°C involving a volume change of approximately 190 L/mol upon going from the physiological-temperature conformer to the low-temperature conformer. This value was determined through previous research from our laboratory using the Clapeyron equation. Our current investigation is to determine whether this protein is fully unfolded or exists as a molten globule below the transition temperature. Our methods for detection are dynamic light scattering, differential scanning calorimetry and circular dichroism. We found that the structure is best characterized as random coil rather than molten globule below 24 °C.