Structural and pharmacological characteristics of chimeric peptides derived from peptide E and beta-endorphin reveal the crucial role of the C-terminal YGGFL and YKKGE motifs in their analgesic properties.
Peptide E (a 25-amino acid peptide derived from proenkephalin A) and beta-endorphin (a 31-amino acid peptide derived from proopiomelanocortin) bind with high affinity to opioid receptors and share structural similarities but induce analgesic effects of very different intensity. Indeed, whereas they possess the same N-terminus Met-enkephalin message sequence linked to a helix by a flexible spacer and a C-terminal part in random coil conformation, in contrast with peptide E, beta-endorphin produces a profound analgesia. To determine the key structural elements explaining this very divergent opioid activity, we have compared the structural and pharmacological characteristics of several chimeric peptides derived from peptide E and beta-endorphin. Structures were obtained under the same experimental conditions using circular dichroism, computational estimation of helical content and/or nuclear magnetic resonance spectroscopy (NMR) and NMR-restrained molecular modeling. The hot-plate and writhing tests were used in mice to evaluate the antinociceptive effects of the peptides. Our results indicate that neither the length nor the physicochemical profile of the spacer plays a fundamental role in analgesia. On the other hand, while the functional importance of the helix cannot be excluded, the last 5 residues in the C-terminal part seem to be crucial for the expression or absence of the analgesic activity of these peptides. These data raise the question of the true function of peptides E in opioidergic systems.
Condamine
Eric
E
European Institute for Peptide Research (IFRMP 23), University of Rouen, France. eric.condamine@ibs.fr
Courchay
Karine
K
Rego
Jean-Claude Do
JC
Leprince
Jérôme
J
Mayer
Catherine
C
Davoust
Daniel
D
Costentin
Jean
J
Vaudry
Hubert
H
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000700:Analgesics / Q000138:chemical synthesis / Q000737:chemistry* / Q000627:therapeutic use*; D000818:Animals; D002942:Circular Dichroism; D004745:Enkephalins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010146:Pain / Q000188:drug therapy; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000627:therapeutic use*; D013329:Structure-Activity Relationship; D001615:beta-Endorphin / Q000737:chemistry*
D000700:Analgesics; D004745:Enkephalins; D010455:Peptides; D001615:beta-Endorphin; C039933:peptide E (adrenal medulla)