Structural Characterization of Growth-Related Translationally Controlled Tumor Protein P23

Abstract

P23, a translationally controlled tumor protein is involved in the interleukin-4 secretion from human basophils and is also known to be an IgE-dependent histamine-releasing factor. However, the precise physiological function and structure of P23 have not been elucidated. In the current study, we constructed the optimal expression and purification protocol of P23 and investigated the secondary structure and structural stability in various conditions. Circular dichroism (CD) investigation showed that the secondary structure of P23 adopts mainly a β-sheet conformation. CD spectroscopy and differential scanning calorimetry revealed that P23 is fairly stable in the pH range of neutral and mild-basic conditions and in the temperature range of 10 - 50℃. Since the thermal stability and the β-sheet content of P23 were decreased by the addition of Ca2+ ion, it could be suggested that Ca2+ ion induces structural change by partially destabilizing the structure of P23. In addition, various NMR experiments were monitored to solve the aggregation of P23. These results will provide the preliminary structural information about P23.