Grace Christy Rani R, Cervini Laura, Gulyas Jozsef, Rivier Jean, Riek Roland
Structural Biology Laboratory, The Salk Institute for Biological Studies, LA Jolla, CA 92037, USA.
Biopolymers. 2007;87(2-3):196-205. doi: 10.1002/bip.20818.
The C-terminally amidated CRF antagonist astressin binds to CRF-R1 or CRF-R2 receptors with low nanomolar affinity while the corresponding astressin-acid has >100 times less affinity. To understand the role of the amide group in binding, the conformations of astressin-amide and astressin-acid were studied in DMSO using NMR techniques. The 3D NMR structures show that the backbones of both analogs prefer an alpha-helical conformation, with a small kink around Gln(26). However, astressin-amide has a well-defined helical structure from Leu(27) to Ile(41) and a conformation very similar to the bioactive conformation reported by our group (Grace et al., Proc Natl Acad Sci USA 2007, 104, 4858-4863). In contrast, astressin-acid has an irregular helical conformation from Arg(35) onward, including a rearrangement of the side chains in that region. This structural difference highlights the crucial role of the C-terminal amidation for stabilization of astressin's bioactive conformation.
C末端酰胺化的促肾上腺皮质激素释放因子（CRF）拮抗剂阿斯特辛以低纳摩尔亲和力与CRF-R1或CRF-R2受体结合，而相应的阿斯特辛酸的亲和力则低100倍以上。为了解酰胺基团在结合中的作用，利用核磁共振技术在二甲基亚砜（DMSO）中研究了阿斯特辛酰胺和阿斯特辛酸的构象。三维核磁共振结构表明，两种类似物的主链均倾向于α-螺旋构象，在Gln(26)周围有一个小扭结。然而，阿斯特辛酰胺从Leu(27)到Ile(41)具有明确的螺旋结构，其构象与我们小组报道的生物活性构象非常相似（Grace等人，《美国国家科学院院刊》2007年，104卷，4858 - 4863页）。相比之下，阿斯特辛酸从Arg(35)起具有不规则的螺旋构象，包括该区域侧链的重排。这种结构差异突出了C末端酰胺化对稳定阿斯特辛生物活性构象的关键作用。
