1apf
From Proteopedia
ANTHOPLEURIN-B, NMR, 20 STRUCTURES
Structural highlights
Function[TXAB_ANTXA] Binds specifically to the sodium channel (site 3) (Nav), thereby delaying its inactivation during signal transduction. Thus it strongly stimulates mammalian cardiac muscle contraction. Does not display phospholipid-binding activity. Anthopleurin-B is the most potent peptide heart stimulator isolated from the sea anemone. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: The polypeptide anthopleurin-B (AP-B) is one of a number of related toxins produced by sea anemones. AP-B delays inactivation of the voltage-gated sodium channel of excitable tissue. In the mammalian heart, this effect is manifest as an increase in the force of contraction. As a result, there is interest in exploiting the anthopleurins as lead compounds in the design of novel cardiac stimulants. Essential to this endeavour is a high-resolution solution structure of the molecule describing the positions of functionally important side chains. RESULTS: AP-B exists in multiple conformations in solution as a result of cis-trans isomerization about the Gly40-Pro41 peptide bond. The solution structure of the major conformer of AP-B has been determined by two-dimensional 1H NMR at pH 4.5 and 25 degrees C. The core structure is a four-stranded, antiparallel beta-sheet (residues 2-4, 20-23, 34-37 and 45-48) and includes several beta-turns (6-9, 25-28, 30-33). Three loops connect the beta-strands, the longest and least well defined being the first loop, extending from residues 8-17. These features are shared by other members of this family of sea anemone toxins. The locations of a number of side chains which are important for the cardiac stimulatory activity of AP-B are well defined in the structures. CONCLUSIONS: We have described the solution structure of AP-B and compared it with that of AP-A, from which it differs by substitutions at seven amino acid positions. It shares an essentially identical fold with AP-A yet is about 10-fold more active. Comparison of the structures, particularly in the region of residues essential for activity, gives a clearer indication of the location and extent of the cardioactive pharmacophore in these polypeptides. Solution structure of the cardiostimulant polypeptide anthopleurin-B and comparison with anthopleurin-A.,Monks SA, Pallaghy PK, Scanlon MJ, Norton RS Structure. 1995 Aug 15;3(8):791-803. PMID:7582896[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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