Perez H D, Holmes R, Vilander L R, Adams R R, Manzana W, Jolley D, Andrews W H
Department of Medicine, University of California, San Francisco 94143.
J Biol Chem. 1993 Feb 5;268(4):2292-5.
We have begun to study the structural requirements for the binding of formyl peptides to their specific receptors. As an initial approach, we constructed C5a-formyl peptide receptor chimeras. Unique (and identical) restriction sites were introduced within the transmembrane domains of these receptors that allowed for the exchange of specific areas. Four types of chimeric receptors were generated. 1) The C5a receptor was progressively substituted by the formyl peptide receptor. 2) The formyl peptide receptor was progressively substituted by the C5a receptor. 3) Specific domains of the C5a receptor were substituted by the corresponding domain of the formyl peptide receptor. 4) Specific domains of the formyl peptide receptor were replaced by the same corresponding domain of the C5a receptor. Wild type and chimeric receptors were transfected into COS 7 cells and their ability to bind formyl peptide determined, taking into account efficiency of transfection and expression of chimeric protein. Based on these results, a ligand binding model is presented in which the second, third, and fourth extracellular (and/or their transmembrane) domains together with the first transmembrane domain form a ligand binding pocket for formyl peptides. It is proposed that the amino-terminal domain plays a role by presumably providing a "lid" to the pocket. The carboxyl-terminal cytoplasmic tail appears to modulate ligand binding by regulating receptor affinity.
我们已开始研究甲酰肽与其特异性受体结合的结构要求。作为初步方法，我们构建了C5a-甲酰肽受体嵌合体。在这些受体的跨膜结构域内引入了独特（且相同）的限制性酶切位点，这使得特定区域能够进行交换。产生了四种类型的嵌合受体。1）C5a受体逐渐被甲酰肽受体取代。2）甲酰肽受体逐渐被C5a受体取代。3）C5a受体的特定结构域被甲酰肽受体的相应结构域取代。4）甲酰肽受体的特定结构域被C5a受体的相同相应结构域替换。将野生型和嵌合受体转染到COS 7细胞中，并测定它们结合甲酰肽的能力，同时考虑转染效率和嵌合蛋白的表达。基于这些结果，提出了一种配体结合模型，其中第二、第三和第四细胞外（和/或其跨膜）结构域与第一个跨膜结构域共同形成甲酰肽的配体结合口袋。有人提出，氨基末端结构域可能通过为口袋提供一个“盖子”发挥作用。羧基末端胞质尾巴似乎通过调节受体亲和力来调节配体结合。
