Astressin-amide and astressin-acid are structurally different in dimethylsulfoxide.
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.
Structural Biology Laboratory, The Salk Institute for Biological Studies, LA Jolla, CA 92037, USA.
Christy Rani R
CR
Grace
Laura
L
Cervini
Jozsef
J
Gulyas
Jean
J
Rivier
Roland
R
Riek
D000577:Amides / Q000737:chemistry; D003346:Corticotropin-Releasing Hormone / Q000737:chemistry* / Q000378:metabolism; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D018019:Receptors, Corticotropin-Releasing Hormone / Q000378:metabolism; D013329:Structure-Activity Relationship; D000099052:CRF Receptor, Type 1
D000577:Amides; C101531:CRF receptor type 2; D010446:Peptide Fragments; D018019:Receptors, Corticotropin-Releasing Hormone; C104416:astressin; D000099052:CRF Receptor, Type 1; D003346:Corticotropin-Releasing Hormone; D004121:Dimethyl Sulfoxide