Folding and Unfolding Behavior of Carboxypeptidase Y Inhibitor (IC) Induced by Temperature and Pressure
Carboxypeptidase Y (CPY) inhibitor, IC, is a heat-stable proteinase inhibitor produced by the yeast Saccharomyces cerevisiae [Matern, H., Hoffmann, M., and Holzer, H. (1974) Proc. Nat. Acad. Sci. USA 71, 4874–4878]. The heat- and pressure-induced unfolding of IC was investigated by means of fluorescence and circular dichroism spectroscopy, in order to better understand the structural basis for its high heat-stability. The heat-induced denaturation showed a two-state transition and was irreversible, while the pressure-induced denaturation showed a multiple-state transition and was completely reversible. The β-sheet of IC was converted into α-helix and random coil structures after heat treatment at 75 ºC whereas the secondary structure content remained unchanged after a pressure treatment at 400 MPa. Thus, it appears that the β-sheet-rich structure of IC is important for its structural stability.
KeywordsPressure Treatment Secondary Structure Content Random Coil Structure General Serine Proteinase Cular Dichroism
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