Structural and thermodynamic analysis of Ipomoelin in complex with metal ions reveal its metal binding properties

• Main Authors: Han-Chen Hsieh, 謝函蓁
• Other Authors: Yi-Sheng Cheng
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/78675962999897501312

碩士 === 國立臺灣大學 === 植物科學研究所 === 103 === Lectins, one of the wound-inducible proteins, play important roles in plants defense systems when plants respond to biotic stress and mechanical wounding. Ipomoelin (IPO), belonging to jacalin-related lectin (JRL) family, is a plant defense protein isolated from sweet potato (Ipomoea batatas cv. Tainung 57). Previous studies identified that IPO can specifically bind to various monocarbohydrates with methyl group. Surprisingly, IPO was found that this protein could bind to not only carbohydrates but also cadmium (Cd). In this study, the structures of IPO in complex with MeMan and cobalt (IPO–MeMan–Co), and in complex with MeMan and cadmium (IPO–MeMan–Cd) are resolved at resolution 1.9 Å. Both of IPO–MeMan–Co and IPO–MeMan–Cd form a tetrameric association and there were metal bind sites adjacent to His 8. Moreover, two metals were chelated in the middle of the tetramer. The results of isothermal titration calorimetry (ITC) indicate that IPO could bind to cobalt, cadmium, zinc, nickel, copper, ferrous (II) and ferric (III), but not to essential metals in plants, such as calcium, magnesium and manganese. The melting point (Tm) of IPO in complex with different metals are analyzed by differential scanning fluorimetry (DSF). The data showed that there was no significant change of Tm while IPO bind to metals, and demonstrated that the metal ion would not provide the stabilized function for IPO structure. Based on the results of IPO and metal ion binding assays, it revealed that IPO would contain the capacity to bind to carbohydrates and heavy metal ions. For further applications of IPO in antipest and antipathogen, IPO would have the potentials toward pesticide.