MECHANISM OF ADENYLATE-CYCLASE ACTIVATION BY CHOLERA TOXIN - INHIBITION OF GTP HYDROLYSIS AT REGULATORY SITE
MECHANISM OF ADENYLATE-CYCLASE ACTIVATION BY CHOLERA TOXIN - INHIBITION OF GTP HYDROLYSIS AT REGULATORY SITE
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DOI：
10.1073/pnas.74.8.3307
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发表时间：
1977-01-01
影响因子：
11.1
通讯作者：
SELINGER, Z
中科院分区：
文献类型：
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作者：
CASSEL, D;SELINGER, Z
用霍乱毒素处理火鸡红细胞膜引起基础和儿茶酚胺刺激的腺苷酸环化酶[ATP焦磷酸裂解酶（环化），EC 4.6.1.1]活性增强。这两种活动都需要GTP的存在。毒素对腺苷酸环化酶活性的影响与抑制儿茶酚胺刺激的鸟苷三磷酸酶活性相一致。鸟苷三磷酸酶的抑制和腺苷酸环化酶活性的增强表现出相同的依赖霍乱毒素浓度，和毒素对这两种活动的影响是依赖于NAD的存在。在调节鸟苷酸位点的连续GTP水解是一种基本的关闭机制，终止腺苷酸环化酶的激活。霍乱毒素抑制鸟苷三磷酸酶的关闭反应，从而引起腺苷酸环化酶的激活。根据这种机制，GTP应该激活毒素处理的腺苷酸环化酶制剂，抗水解类似物鸟苷5”-（β，.伽马亚氨基）三磷酸[Gpp（NH）p]。在异丙肾上腺素存在下，毒素处理的腺苷酸环化酶被GTP或Gpp（NH）p最大程度地激活，而未用毒素处理的腺苷酸环化酶被激素加GTP刺激至仅为激素加Gpp（NH）p所获得的活性的1/5。被异丙肾上腺素加GTP激活的毒素处理的腺苷酸环化酶在较长时间内保持活性（半衰期为3分钟），随后加入β-肾上腺素能阻滞剂心得安本地酶是难治性普萘洛尔只有当激活GPP（NH）p，但不是GTP。
Treatment of turkey erythrocyte membranes with cholera toxin caused an enhancement of the basal and catecholamine-stimulated adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activities. Both activities required the presence of GTP. The toxin effect on the adenylate cyclase activity coincided with an inhibition of the catecholamine-stimulated guanosinetriphosphatase activity. Inhibition of the guanosinetriphosphatase and enhancement of the adenylate cyclase activity showed the same dependence on cholera toxin concentrations, and the effect of the toxin on both activities was dependent on the presence of NAD. Continuous GTP hydrolysis at the regulatory guanyl nucleotide site is an essential turn-off mechanism, terminating activation of the adenylate cyclase. Cholera toxin inhibits the turn-off guanosinetriphosphatase reaction and thereby causes activation of the adenylate cyclase. According to this mechanism GTP should activate the toxin-treated preparation of adenylate cyclase, as does the hydrolysis-resistant analog guanosine 5''-(.beta.,.gamma.-imino)triphosphate [Gpp(NH)p]. The toxin-treated adenylate cyclase was maximally activated, in the presence of isoproterenol, by GTP or Gpp(NH)p, while adenylate cyclase not treated with toxin was stimulated by hormone plus GTP to only 1/5 of the activity achieved with hormone plus Gpp(NH)p. The toxin-treated adenylate cyclase activated by isoproterenol plus GTP remained active for an extended period (half-time of 3 min) upon subsequent addition of the .beta.-adrenergic blocker, propranolol. The native enzyme was refractory to propranolol only if activated by Gpp(NH)p but not by GTP.