Di Paolo E, De Neef P, Moguilevsky N, Petry H, Bollen A, Waelbroeck M, Robberecht P
Department of Biochemistry and Nutrition, Faculty of Medicine, Nivelles, Université Libre de Bruxelles, Brussels, Belgium.
FEBS Lett. 1998 Mar 13;424(3):207-10. doi: 10.1016/s0014-5793(98)00175-6.
The secretin amino-terminal residues are essential for high affinity binding to its cognate receptor and for its biological activity. Mutation of the [Asp3] residue of secretin to [Asn3] decreased the ligand's affinity for the rat wild-type receptor 100-300-fold. Receptor mutations in the transmembrane 2 domain and the beginning of the first extracellular loop allowed the identification of three residues involved in recognition of the [Asp3] residue: D174, K173 and R166. Mutation of K173 and D174 not only reduced the secretin and [Asn3]secretin affinities, but also changed the receptor's selectivity as judged by a decreased secretin and [Asn3]secretin potency ratio. The most striking effect was observed when R166 was mutated to Q, D or L. This led to receptors with a very low affinity for secretin but an up to 10-fold higher affinity than the wild-type receptor for [Asn3]secretin. This suggested that R166, highly conserved in that subgroup of receptor, is a major determinant for the recognition of the [Asp3] of the ligand.
促胰液素的氨基末端残基对于其与同源受体的高亲和力结合及其生物学活性至关重要。促胰液素的[Asp3]残基突变为[Asn3]会使配体对大鼠野生型受体的亲和力降低100 - 300倍。跨膜2结构域和第一个细胞外环起始处的受体突变使得能够鉴定出参与识别[Asp3]残基的三个残基：D174、K173和R166。K173和D174的突变不仅降低了促胰液素和[Asn3]促胰液素的亲和力，而且从促胰液素和[Asn3]促胰液素效价比降低判断，还改变了受体的选择性。当R166突变为Q、D或L时观察到最显著的效应。这导致受体对促胰液素的亲和力非常低，但对[Asn3]促胰液素的亲和力比野生型受体高多达10倍。这表明在该受体亚组中高度保守的R166是识别配体[Asp3]的主要决定因素。
