A proton nuclear magnetic resonance study of the antihypertensive and antiviral protein BDS-I from the sea anemone Anemonia sulcata: sequential and stereospecific resonance assignment and secondary structure

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Abstract
The sequential resonance assignment of the 1H NMR spectrum of the antihypertensive and antiviral protein BDS-I from the sea anemone Anemonia sulcata is presented. This is carried out with two-dimensional NMR techniques to identify through-bond and through-space (< 5 .ANG.) connectivities. Added spectral complexity arises from the fact that the sample is an approximately 1:1 mixture of two BDS-I isoproteins, (Leu-18)-BDS-I and (Phe-18)-BDS-I. Complete assignments, however, are obtained, largely due to the increased resolution and sensitivity afforded at 600 MHz. In addition, the stereospecific assignment of a large number of .beta.-methylene protons is achieved from an analysis of the pattern of 3J.alpha..beta. coupling constants and the relative magnitudes of intraresidue NOEs involving the NH, C.alpha.H, and C.beta.H protons. Regular secondary structure elements are deduced from a qualitative interpretation of the nuclear Overhauser enhancement, 3JHN.alpha. coupling constant, and amide NH exchange data. A triple-stranded antiparallel .beta.-sheet is found to be related to that found in partially homologous sea anemone polypeptide toxins.

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