→信号传导的分子开关 OFF SIGNAL SIGNAL OFF N GDP kinas GTP ATP phosphatase GTP GDP activates inactivates binding hydrolysis activates inactivates DP GTP ON ON GTP SIGNAL SIGNAL OUT OUT (A)E SIGNALING BY PHOSPHORYLATION (B)E SIGNALING BY GTP-BINDING PROTEIN 分子开关¨信号传导的分子开关 分子开关