Solution conformation of a synthetic fragment of human pituitary growth hormone. Two-dimensional NMR of an alpha-helical dimer.
Circular dichroism and two-dimensional NMR spectra indicate that a peptide fragment consisting of the first 28 residues from the N-terminus of human growth hormone (hGH 1-28) has considerable alpha-helical structure. The peptide, (1) H-Phe-Pro-Thr-Ile-Pro-Leu-Ser-Arg-Leu-Phe-Asp-Asn-Ala-Met-Leu-Arg-Ala-Hi s-Arg- Leu-His-Gln-Leu-Ala-Phe-Asp-Thr-Tyr-OH (28), was synthesized on an automated peptide synthesizer using the Merrifield solid-phase method. The peptide can be modeled as an amphiphilic helix, and the unusual stability of the alpha-helix in aqueous solution is suggested to be attributable to formation of a dimer of alpha-helices. Most of the 1H NMR signals were assigned through pure absorption phase COSY/NOESY and single- and double-relay COSY 2D NMR spectra by using the sequential assignment methodology. The NOEs were large and negative, suggesting that the peptide was not a random coil and that it existed in solution primarily as a large, fairly rigid macromolecule, consistent with the dimer structure. A network of N alpha Hi-N alpha Hi+1 NOESY crosspeaks is observed from residues 13 to 18 as are several other crosspeaks which indicate that the peptide has considerable alpha-helical structure between residues 8 and 24. In addition, gel filtration of the peptide is consistent with a dimer structure, presumably involving packing of the two hydrophobic faces of the amphiphilic alpha-helices.
Roongta
V
V
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907.
Powers
R
R
Jones
C
C
Beakage
M J
MJ
Shields
J E
JE
Gorenstein
D G
DG
D000595:Amino Acid Sequence; D013006:Growth Hormone / Q000138:chemical synthesis; D006801:Humans; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D010446:Peptide Fragments / Q000138:chemical synthesis; D011487:Protein Conformation
D046911:Macromolecular Substances; D010446:Peptide Fragments; D013006:Growth Hormone