The forgotten serine -: A critical role for Ser-2035.42 in ligand binding to and activation of the β2-adrenergic receptor
The forgotten serine -: A critical role for Ser-2035.42 in ligand binding to and activation of the β2-adrenergic receptor
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DOI：
10.1074/jbc.m002092200
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发表时间：
2000-12-01
影响因子：
4.8
通讯作者：
Javitch, JA
中科院分区：
文献类型：
--
作者：
Liapakis, G;Ballesteros, JA;Javitch, JA
先前在β（2）-肾上腺素能受体中的工作证明了第五跨膜片段中的Ser-204和Ser-207分别与儿茶酚胺激动剂的间位-OH和对位-Os之间的关键相互作用（Strader，C. D、Candelore，M，R.，Hill，W.美国，锡加尔岛美国，和狄克逊，R，A.（1989）J.Biol.Chem.264，13572 - 13578）。在β（2）-肾上腺素能受体中使用取代的半胱氨酸可接近性方法，我们发现除了Ser-204和Ser-207之外，Ser-203也可接近于结合位点缝隙的表面，并被结合的激动剂封闭。Ser-203突变为Ala、瓦尔或Cys降低了含有间位-OH的激动剂的结合亲和力和腺苷酸环化酶激活效力，而它们的亲和力和效力在很大程度上通过Ser-203突变为Thr而保留，这在该位置保持了OH。因此，Ser-203和Ser-204似乎与儿茶酚胺的间位-OH相互作用，可能通过分叉的H键。此外，在位置203处的OH的去除导致拮抗剂与其杂环结构中的氮的亲和力的显著损失。最大的效果被认为与吲哚洛尔，部分激动剂，这表明杂环和Ser-203之间的H键可能在部分激动中发挥作用。与此相反，拮抗剂，如普萘洛尔或alprenolol，它具有环状结构，没有H-键合能力的亲和力，Ser-203突变后不变。
Previous work in the beta (2)-adrenergic receptor demonstrated critical interactions between Ser-204 and Ser-207 in the fifth membrane-spanning segment and the meta-OH and para-Os, respectively, of catecholamine agonists (Strader, C. D., Candelore, M, R., Hill, W. S., Sigal, I. S., and Dixon, R, A. (1989) J. Biol. Chem. 264, 13572-13578). Using the substituted cysteine accessibility method in the beta (2)-adrenergic receptor, we have found that in addition to Ser-204 and Ser-207, Ser-203 is also accessible on the surface of the binding-site crevice and is occluded by bound agonist. Mutation of Ser-203 to Ala, Val, or Cys reduced the binding affinity and adenylyl cyclase-activating potency of agonists containing a meta-OH, whereas their affinities and potencies were largely preserved by mutation of Ser-203 to Thr, which maintained an OH at this position. Thus both Ser-203 and Ser-204 appear to interact with the meta-OH of catecholamines, perhaps through a bifurcated H bond. Furthermore, the removal of the OH at position 203 led to a significant loss of affinity of antagonists with nitrogen in their heterocyclic ring structure. The greatest effect was seen with pindolol, a partial agonist, suggesting that a H bond between the heterocyclic ring and Ser-203 may play a role in partial agonism. In contrast, the affinities of antagonists such as propranolol or alprenolol, which have cyclic structures without H-bonding capability, were unaltered after mutation of Ser-203.