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Sticholysin I (StnI) is an actinoporin produced by the sea anemone Stichodactyla helianthus that binds biological and model membranes forming oligomeric pores. Both a surface cluster of aromatic rings and the N-terminal region are involved in pore formation. To characterize the membrane binding by StnI, we have studied by 1H-NMR the environment of these regions in water and in the presence of membrane-mimicking micelles. Unlike other peptides from homologous actinoporins, the synthetic peptide corresponding to residues 1–30 tends to form helix in water and is more helical in either trifluoroethanol or dodecylphosphocholine (DPC) micelles. In these environments, it forms a helix-turn-helix motif with the last α-helical segment matching the native helix-α1 (residues 14–24) present in the complete protein. The first helix (residues 4–9) is less populated and is not present in the water-soluble protein structure. The characterization of wild-type StnI structure in micelles shows that the helix-α1 is maintained in its native structure and that this micellar environment does not provoke its detachment from the protein core. Finally, the study of the aromatic resonances has shown that the motional flexibility of specific rings is perturbed in the presence of micelles. On these bases, the implication of the aromatic rings of Trp-111, Tyr-112, Trp-115, Tyr-132, Tyr-136, and Tyr-137, in the interaction between StnI and the micelle is discussed. Based on all the findings, a revised model for StnI interaction with membranes is proposed, which accounts for differences in its behavior as compared with other highly homologous sticholysins. Proteins 2010., Spanish Ministerio de Ciencia e Innovación; Grant numbers: CTQ2008-00080/BQU, BFU2009-10185

Resumen del trabajo presentado en la XXIII International Conference on Magnetic Resonance in Biological Systems, celebrada en San Diego, California (Estados Unidos) del 24 al 29 de agosto de 2008.

Resumen del póster presentado en la IV Reunión bienal del grupo de especialización de RMN de la RSEQ. I Reunión Ibérica de RMN (2008), celebrada en Sevilla (España) del 21 al 24 de septiembre de 2008.