Blomenröhr M, Bogerd J, Leurs R, Schulz R W, Tensen C P, Zandbergen M A, Goos H J
Research Group for Comparative Endocrinology, University of Utrecht, Utrecht, The Netherlands.
Biochem Biophys Res Commun. 1997 Sep 18;238(2):517-22. doi: 10.1006/bbrc.1997.7331.
Mammalian gonadotropin-releasing hormone receptors (GnRH-Rs) differ from other G protein-coupled receptors in lacking the intracellular C-terminus and in showing an exchange of two otherwise highly conserved Asp (D) and Asn (N) residues in transmembrane domains (TMD) 2 and 7, respectively. However, the first GnRH-R characterized from a nonmammalian vertebrate, the African catfish, does contain an intracellular C-terminus and has D residues in TMD 2 and 7. The functional relevance of these structural features was analysed with D90N321, N90D321, N90N321 and C-terminally truncated mutant catfish GnRH-Rs. An antiserum raised against the recombinant extracellular domain of the wild-type catfish GnRH-R detected all mutant receptors at the cell surface of transiently transfected 293T cells. However, only the D90N321 mutant specifically bound GnRHs and activated signal transduction in response to GnRHs; all other mutants were inactive in both respects. We conclude that the catfish GnRH-R differs from the mammalian GnRH-Rs in that both the C-terminal domain and D90 in TMD 2 are important for receptor functioning.
哺乳动物促性腺激素释放激素受体（GnRH-Rs）与其他G蛋白偶联受体不同，它缺乏细胞内C末端，并且在跨膜结构域（TMD）2和7中分别存在两个原本高度保守的天冬氨酸（D）和天冬酰胺（N）残基的交换。然而，首个从非哺乳动物脊椎动物非洲鲶鱼中鉴定出的GnRH-R确实含有细胞内C末端，并且在TMD 2和7中具有D残基。利用D90N321、N90D321、N90N321和C末端截短的突变型鲶鱼GnRH-Rs分析了这些结构特征的功能相关性。一种针对野生型鲶鱼GnRH-R重组细胞外结构域产生的抗血清在瞬时转染的293T细胞表面检测到了所有突变受体。然而，只有D90N321突变体特异性结合GnRHs并响应GnRHs激活信号转导；所有其他突变体在这两方面均无活性。我们得出结论，鲶鱼GnRH-R与哺乳动物GnRH-Rs的不同之处在于，C末端结构域和TMD 2中的D90对受体功能均很重要。
