Secondary Structure in Sea Anemone Polypeptides: A Proton Nuclear Magnetic Resonance Study

Abstract

Elements of secondary structure in the sea anemone polypeptides anthopleurin A and Anemonia sulcata toxin I have been defined with the following nuclear magnetic resonance (NMR) spectroscopic data: the pattern of nuclear Overhauser enhancement (NOE) connectivities observed in two-dimensional NMR spectra for protons along the polypeptide backbone, NOE's between protons on separate strands of the polypeptide backbone, peptide NH exchange rates, and NH-Hα spin-spin coupling constants. These two polypeptides contain a region of four short strands of antiparallel β-sheet but little or no α-helix. This region of β-sheet brings the aromatic rings of Trp-23 and -33 into close proximity to form the n..