水稻OsGAP1 C2结构域中对钙离子的结合能力强于对钾离子

钙离子作为植物细胞的第二信使，广泛参与植物应对不同逆境胁迫的信号调控过程。水稻G蛋白促进蛋白1（Oryza sativa GTPase activating protein 1, OsGAP1）包含1个C2结构域，而含C2结构域的蛋白质是一类钙离子结合蛋白质，受钙信号的调控。本研究鉴定了水稻OsGAP1的由5个保守性天冬氨酸残基组成的阳离子结合区域。该区域可结合2个钙离子或者钾离子，且其结合钙离子的强度高于其结合钾离子的强度，但是不能结合镁离子。当将其中2个保守的天冬氨酸残基(Asp-23和Asp-28)突变为丙氨酸后，其对钙离子的结合能力减弱。对OsGAP1 C2结构域阳离子结合区域结合金属离子能力的研究，有助于加深对钙信号调控蛋白质的认识，为其在农业生产中的应用提供理论依据。

The OsGAP1 C2 Domain of Rice Has Higher Binding Affinity for Ca 2+ Than for K+

As a second messenger, calcium is widely involved in the signal regulation in response to different environmental stresses in plants. Oryza sativa GTPase-activating protein 1 (OsGAP1) contains a C2 domain, and the C2 domain-containing proteins are a class of calcium-binding proteins mediated by calcium signaling. In the present study, a cation-binding site of OsGAP1 consisting of five conserved aspartic acid residues has been identified. The region can bind two calcium or potassium ions, but not magnesium ions. The strength of its binding to calcium ion is higher than that of binding to potassium ion. When two of the conserved aspartic acid residues (Asp-23 and Asp-28) were mutated to alanine, the binding strength of calcium ions was reduced. The study of the cation binding site in the OsGAP1 C2 domain would help us to deepen the understanding of the calcium signaling proteins and provide some basic theories for its application in the agricultural ecosystem.