研究生教學(xué) 細(xì)胞信息傳遞 第八節(jié) 信號(hào)轉(zhuǎn)導(dǎo)與醫(yī)學(xué)-文庫吧
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【正文】 btypes ? binds GTP/GDP ? activation of 2nd mess. ? less variability ? also activates 2nd mess. ? ? ? G蛋白亞單位 （ Gprotein subunits） ? Three subunits 主要類型及功能： Gs:(Stimulatory G protein) (+)腺苷酸環(huán)化酶 cAMP Gi:( inhibitory G protein ) ()腺苷酸環(huán)化酶 cAMP Gq:活化磷脂酶 Cβ ? G蛋白亞單位的聚合與解聚 第四節(jié) G蛋白耦聯(lián)受體介導(dǎo)的 下游信號(hào)體系 信號(hào)分子 受體 G蛋白 腺苷酸環(huán)化酶 A 激 酶 Pro Prop 生理功能調(diào)節(jié) 一、 G蛋白 耦聯(lián)受體與腺苷酸環(huán)化酶 The sequence of events by which a hormone activates cAMP signaling AC h o r m o n e sig n a l o u t s i d e G P CR p la sm a m e m b r a n e GT P GDP A T P cA M P + P Pi ?? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ??????????? c y to so l ?G D P ? ? ? ? ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ???? ? G T P 1. Initially Ga has bound GDP, and αβamp。 γ subunits are plexed together. 2. Hormone binding to a 7helix receptor (GPCR) causes a conformational change in the receptor that is transmitted to the G protein. The nucleotidebinding site on Ga bees more accessible to the cytosol, where [GTP] [GDP]. Ga releases GDP amp。 binds GTP (GDPGTP exchange). 3. Substitution of GTP for GDP causes another conformational change in Ga. GaGTP dissociates from the inhibitory βγ plex amp。 can now bind to and activate Adenylate Cyclase. 4. Adenylate Cyclase, activated by GaGTP, catalyzes synthesis of cAMP. 5. Protein Kinase A (cAMP Dependent Protein Kinase) catalyzes phosphorylation of various cellular proteins, altering their activity. cAMP： ATP 腺苷酸環(huán)化酶
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