Structural Analysis of the Carboxyl Terminal Peptide From Human Chorionic Gonadotropin β-Subunit by Two-Dimensional Nuclear Magnetic Resonance Spectroscopy

PROBLEM : Vaccines that target human chorionic gonadotropin (hCG) might be made more effective through greater understanding of the solution three-dimensional structure and behavior of the hormone. METHOD : A 37-amino acid carboxyl terminal peptide of the hCG beta subunit was synthesized, purified, and analyzed by two-dimensional nuclear magnetic resonance spectroscopy. RESULTS : Double-quantum filtered correlated spectroscopy data on the peptide in water at 4°C reveals 27 multiplets in the peptide fingerprint region, as expected. A nuclear Overhauser effect spectroscopy spectrum shows several intraresidual peaks in the amide region but lacks clearly assignable interresidual signals. CONCLUSION : By itself in water the carboxyl terminal peptide of hCG lacks defined secondary structure elements and is thus likely a random coil. The presence of beta turns appears possible although neither their existence nor their localization can be confirmed.