Structure-function studies on the cyclic peptide MT-II, lactam derivative of alpha-melanotropin

Citation
Ma. Bednarek et al., Structure-function studies on the cyclic peptide MT-II, lactam derivative of alpha-melanotropin, PEPTIDES, 20(3), 1999, pp. 401-409
Citations number
35
Categorie Soggetti
Biochemistry & Biophysics
Journal title
PEPTIDES
ISSN journal
01969781 → ACNP
Volume
20
Issue
3
Year of publication
1999
Pages
401 - 409
Database
ISI
SICI code
0196-9781(1999)20:3<401:SSOTCP>2.0.ZU;2-W
Abstract
The alanine-substituted and the retro, enantio, and retro-enantio analogs o f MT-II, a potent agonist at melanocortin (MC) receptors, were prepared by solid-phase synthesis and evaluated for their ability to bind and activate human MC3, MC4, and MC5 receptors. Replacement of His with Ala resulted in [Ala(6)]-MT-II with affinity and agonist potency at human MC3, MC4, and MC5 receptors similar to MT-II. Substitution of Arg with Ala gave compound 100 -fold less potent than MT-II, but replacement of Phe or Trp with Ala led to inactive compounds (at the micromolar concentrations). The significant dro p of potency of the retro, enantio, and retro-enantio analogs of MT-II, dem onstrated a crucial role of side-chain topology, and to a lesser degree, of peptide backbone in interactions of MT-II with the melanocortin receptors. The nuclear magnetic resonance analysis of MT-II suggested involvement of Phe and Arg residues in H-bonds stabilizing the bent conformations of the p eptide backbone. (C) 1999 Elsevier Science Inc. All rights reserved.