Nuclear magnetic resonance studies of thyrotropin-releasing hormone (TRH) and analogues incorporating D-histidine and 4-hydroxy-L-proline.
NMR studies have been used to examine conformational effects in thyrotropin-releasing hormone (TRH), the epimer incorporating D-His, and their analogues where trans- and cis-4-hydroxy-L-proline replace L-proline (Pro). In all six compounds the observed overall conformation of the major conformer around the Pro-His amide bond, and the observed increase of the cis/trans ratio between the conformers when L-His is replaced by D-His, can be accommodated by assuming that a ten-membered ring is formed by hydrogen bonding between the N-H of the Pro carboxamide function and the N pi-atom of the His imidazole nucleus.
Aksnes
D W
DW
Department of Chemistry, University of Bergen, Norway.
Athanassopoulos
C
C
Magafa
V
V
Aaberg
A
A
Francis
G W
GW
Papaioannou
D
D
D000595:Amino Acid Sequence; D006639:Histidine; D006909:Hydroxyproline; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011487:Protein Conformation; D013973:Thyrotropin-Releasing Hormone / Q000737:chemistry*
D006639:Histidine; D013973:Thyrotropin-Releasing Hormone; D006909:Hydroxyproline