A cyclic beta-strand tripeptide with an alpha-helix like CD spectrum.
A protein alpha-helix is defined by 3.6 amino acids per turn. Cyclization of the tripeptide Alanine-Leucine-Glutamate through a side chain to the N-terminus lactam bond produces cyclo-(1,3)-[ALE]-NH(2) which displays a circular dichroism spectrum typical of an alpha-helix backbone. However, proton NMR spectra show a novel cyclic peptide featuring two non-hydrogen-bonded antiparallel beta-strands connected by an Ala-Leu cis-amide bond. This example highlights that the common practice of characterizing alpha-helices by CD spectra alone can be misleading.
Driver
Russell W
RW
Division of Chemistry and Structural Biology, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld 4072, Australia.
Hoang
Huy N
HN
Abbenante
Giovanni
G
Fairlie
David P
DP
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003500:Cyclization; D008958:Models, Molecular; D015394:Molecular Structure; D010456:Peptides, Cyclic / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013237:Stereoisomerism
D010456:Peptides, Cyclic