Mantamadiotis T, Baldwin G S
Ludwig Institute for Cancer Research, Royal Melbourne Hospital, Victoria, Australia.
Biochem Biophys Res Commun. 1994 Jun 30;201(3):1382-9. doi: 10.1006/bbrc.1994.1856.
The related rat cholecystokinin (CCK)-A and gastrin/CCK-B receptors can be selectively blocked by the antagonists L364718 and L365260, respectively. In order to determine receptor domains which are important in conferring specificity for L365260 and L364718 we constructed by overlap-PCR a rat gastrin/CCK-B receptor chimaera which contained the seventh transmembrane domain of the rat CCK-A receptor. Receptor binding assays on transiently transfected COS cells demonstrated a selective reduction in the affinity of the chimaeric receptor for L364718, so that the L365260 and L364718 affinities were of a similar order. Since the chimaera differs from the wild-type gastrin/CCK-B receptor by only six amino acids we conclude that one or more of these six amino acids contributes to L364718 binding and that the affinity determinants of L365260 and L364718 must, at least in part, be different. Furthermore, the affinity of the chimaera for gastrin is essentially the same as the gastrin/CCK-B receptor, indicating that the six different amino acids probably do not contribute to peptide agonist binding.
相关的大鼠胆囊收缩素（CCK）-A受体和胃泌素/CCK-B受体可分别被拮抗剂L364718和L365260选择性阻断。为了确定对L365260和L364718具有特异性的受体结构域，我们通过重叠PCR构建了一种大鼠胃泌素/CCK-B受体嵌合体，该嵌合体包含大鼠CCK-A受体的第七跨膜结构域。对瞬时转染的COS细胞进行的受体结合试验表明，嵌合受体对L364718的亲和力选择性降低，因此L365260和L364718的亲和力处于相似水平。由于该嵌合体与野生型胃泌素/CCK-B受体仅相差六个氨基酸，我们得出结论，这六个氨基酸中的一个或多个对L364718的结合有贡献，并且L365260和L364718的亲和力决定因素至少部分是不同的。此外，嵌合体对胃泌素的亲和力与胃泌素/CCK-B受体基本相同，这表明这六个不同的氨基酸可能对肽激动剂的结合没有贡献。
