School of Biological Sciences, University of Auckland, Auckland, New Zealand.
Peptides. 2012 Jul;36(1):137-41. doi: 10.1016/j.peptides.2012.04.011. Epub 2012 Apr 21.
Adrenomedullin (AM) is a peptide, which is important for vascular development. There is much interest in the clinical potential of its receptors. The mode of AM binding to its receptors is poorly understood. Previous studies have identified amino acid Glu74, which is found in the receptor activity-modifying protein (RAMP3) subunit of the AM(2) receptor as important for high affinity AM interactions with this receptor. Its reciprocal residue in RAMP1 (Trp) impedes AM interactions in the closely related human calcitonin gene-related peptide (CGRP) receptor. The Glu is conserved in RAMP3 across species, supporting its role in contributing to AM binding. We mutated this residue in rat and mouse RAMP3 to Ala, Lys and Trp to determine its function in rodent AM(2) receptors. Only the Trp substitution in mouse RAMP3 produced a substantial reduction in AM potency. However, mutation of the Lys found in rat RAMP1 to Glu enhanced AM potency. Although Glu is highly conserved in RAMP3, this work suggests that it may only make a small or indirect contribution to AM interactions. Nevertheless, the equivalent amino acid in RAMP1 may serve to impair high affinity AM interactions.
肾上腺髓质素（AM）是一种对血管发育很重要的肽。人们对其受体的临床潜力非常感兴趣。AM 与其受体结合的模式尚未得到充分理解。先前的研究已经确定了在 AM（2）受体的受体活性修饰蛋白（RAMP3）亚基中发现的氨基酸 Glu74 对于 AM 与该受体的高亲和力相互作用很重要。在密切相关的人类降钙素基因相关肽（CGRP）受体中，其在 RAMP1 中的对应残基（Trp）会阻碍 AM 相互作用。该 Glu 在跨物种的 RAMP3 中是保守的，支持其在促进 AM 结合中的作用。我们将该残基突变为大鼠和小鼠 RAMP3 的 Ala、Lys 和 Trp，以确定其在啮齿动物 AM（2）受体中的功能。只有在小鼠 RAMP3 中的 Trp 取代产生了 AM 效力的实质性降低。然而，在大鼠 RAMP1 中发现的 Lys 突变为 Glu 增强了 AM 的效力。尽管 Glu 在 RAMP3 中高度保守，但这项工作表明它可能仅对 AM 相互作用做出微小或间接的贡献。尽管如此，RAMP1 中的等效氨基酸可能会损害 AM 的高亲和力相互作用。
