One‐dimensional and two‐dimensional photochemically induced dynamic nuclear polarisation (photo‐CIDNP) nuclear magnetic resonance spectra have been recorded for the sea‐anemone polypeptide cardiac stimulants anthopleurin‐A and Anemonia sulcata toxins I and II. In anthopleurin‐A and toxin II, all three Trp residues are accessible to the flavin dye, although Trp‐23 in anthopleurin‐A shows a weaker photo‐CIDNP response than Trp‐33 and Trp‐45. Tyr‐25 in anthopleurin‐A also shows a strong response. In toxin I, Trp‐23, Trp‐33 and Tyr‐45 (which replaces Trp in this molecule) are accessible to the dye. The pH dependences of the photo‐CIDNP spectra of all three polypeptides have been examined. The response of Trp‐33 increases significantly with pH. The two His residues of anthopleurin‐A and toxin II display a response in their imidazole forms, but not their imidazolium forms. The surface accessibilities of Trp‐23 and Trp‐33 are discussed in relation to the interaction of these polypeptides with the Na+ channel.
|Number of pages||4|
|Journal||European Journal of Biochemistry|
|Publication status||Published - 1986|