title: beta-Endorphin: demonstration of a tertiary structure in aqueous solution.
abstract: Difference spectra generated during thermolysin digestion of camel beta-endorphin at pH 8.2 or at pH 6.5 indicate rapid blue shifting of the near-UV absorption bands of the NH2-terminal tyrosine. A similar spectral change is not observed for the NH2-terminal tyrosine in [Met]enkephalin when it is digested under similar conditions. These results suggest that enzymatic digestion destroys or alters some structural interaction between the NH2-terminal tyrosyl residue of the endorphin and a residue(s) within the COOH-terminal segment of the molecule. Peptide mapping of the digest as a function of time suggests that cleavage of the bond linking the alanine-21 and isoleucine-22 residues produces most of the observed effect. These data provide evidence for the existence of a tertiary structure for beta-endorphin in aqueous solutions.
mesh_terms: D004723:Endorphins / Q000032:analysis; D004744:Enkephalin, Methionine; D004745:Enkephalins; D006863:Hydrogen-Ion Concentration; D010446:Peptide Fragments / Q000032:analysis; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D001615:beta-Endorphin
chemical_list: D004723:Endorphins; D004745:Enkephalins; D010446:Peptide Fragments; D004744:Enkephalin, Methionine; D001615:beta-Endorphin