Infrared spectroscopic evidence of conformational transitions of an atrial natriuretic peptide.

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Abstract
The conformational properties of the atrial natriuretic peptide atriopeptin III were investigated by Fourier-transform infrared spectroscopy. Infrared spectra in the amide I region were analyzed quantitatively using deconvolution and band-fitting procedures. According to this analysis, in aqueous solution the monomeric peptide has a random structure. Binding to bilayer vesicles of dimyristoyl phosphatidylglycerol results in drastic conformational changes. The lipid-complexed atriopeptin III adopts a highly ordered structure of predominantly .beta.-sheets. A transition to a similar, but not identical, .beta.-structure occurs upon self-association of the peptide. The results of model experiments suggest that the binding of this atrial peptide to the target cell membrane is associated with the induction of .beta.-sheet structure and that it is this latter conformation that is predominant in the active form of the hormone.