Effect of Mg2+ on the Structure and Function of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase
- 181 Downloads
Mg2+ in various concentrations was added to purified Rubisco in vitro to gain insight into the mechanism of molecular interactions between Mg2+ and Rubisco. The enzyme activity assays showed that the reaction between Rubisco and Mg2+ was two order, which means that the enhancement of Rubisco activity was accelerated by low concentration of Mg2+ and slowed by high concentration of Mg2+. The kinetics constant (K m) and V max was 1.91 μM and 1.13 μmol CO2 mg−1 protein∙min−1, respectively, at a low concentration of Mg2+, and 3.45 μM and 0.32 μmol CO2∙mg−1 protein∙min−1, respectively, at a high concentration of Mg2+. By UV absorption and fluorescence spectroscopy assays, the Mg2+ was determined to be directly bound to Rubisco; the binding site of Mg2+ to Rubisco was 0.275, the binding constants (K A) of the binding site were 6.33 × 104 and 5.5 × 104 l·mol−1. Based on the analysis of the circular dichroism (CD) spectra, it was concluded that the binding of Mg2+ did not alter the secondary structure of Rubisco, suggesting that the observed enhancement of Rubisco carboxylase activity was caused by a subtle structural change in the active site through the formation of the complex with Mg2+.
KeywordsMg2+ Rubisco Enzyme kinetics Spectral characteristic
This work was supported by the National Natural Science Foundation of China (grant no. 30470150, 20671067) and by the Jiangsu Province Universities Natural Science Foundation (grant no. 06KJB180094).
- 10.Lorimer GH, Miziorko HM (1980) Carbamate formation in the 2 amine group of a lysyl residue as the basis for the activation of ribulose-1,5-bisphosphate carboxylase by CO2 and Mg2+. Biochem 19(6):5321–5328Google Scholar
- 13.von Caemmerer S, Millgate A, Farquhar GD, Furbank RT (1997) Reduction of ribulose-1,5-bisphosphate carboxylase/oxygenase by antisense RNA in the C4 plant Flaveria bidentis leads to reduced assimilation rates and increased carbon isotope discrimination. Plant Physiol 113:469–477Google Scholar
- 15.Chen WJ, Gu YH, Wang SB, Zhao GW (2000) Effects of lanthanum on activity of RuBPase in tobacco. J Rare Earth 18(3):258–261Google Scholar
- 17.Sugiyama T, Nakayama N, Ogawa M, Akazawa T, Oda T (1968) Structure and function of chloroplast proteins: effect of ρ-chloromercuribenzoate treatment on the ribulose-1,5-bisphosphate carboxylase/oxygenase activity of spinach leaf fraction protein. Arch Biochem Biophys 125:98–106PubMedCrossRefGoogle Scholar
- 21.Lakowicz JR (1983) Principles of fluorescence spectroscopy. Plenum, New York (p 258)Google Scholar