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The Isolation of New Pore-Forming Toxins from the Sea Anemone Actinia fragacea Provides Insights into the Mechanisms of Actinoporin Evolution

Department of Bioengineering, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
Department of Biochemistry and Molecular Biology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
Instituto Biofisika (CSIC, UPV/EHU), Parque Científico de la UPV/EHU, Barrio Sarriena s/n, 48940 Leioa (Bizkaia), Spain
Instituto Superior de Investigaciones Biológicas (INSIBIO, CONICET-UNT) e Instituto de Química Biológica “Dr. Bernabé Bloj,” Facultad de Bioquímica, Química y Farmacia, Universidad Nacional de Tucumán, Chacabuco 461, T4000 San Miguel de Tucumán, Argentina
Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan
Department of Global Healthcare, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
Authors to whom correspondence should be addressed.
Toxins 2019, 11(7), 401;
Received: 31 May 2019 / Revised: 29 June 2019 / Accepted: 5 July 2019 / Published: 10 July 2019
(This article belongs to the Special Issue Pore-Forming Toxins (PFTs): Never Out of Fashion)
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Random mutations and selective pressure drive protein adaptation to the changing demands of the environment. As a consequence, nature favors the evolution of protein diversity. A group of proteins subject to exceptional environmental stress and known for their widespread diversity are the pore-forming hemolytic proteins from sea anemones, known as actinoporins. In this study, we identified and isolated new isoforms of actinoporins from the sea anemone Actinia fragacea (fragaceatoxins). We characterized their hemolytic activity, examined their stability and structure, and performed a comparative analysis of their primary sequence. Sequence alignment reveals that most of the variability among actinoporins is associated with non-functional residues. The differences in the thermal behavior among fragaceatoxins suggest that these variability sites contribute to changes in protein stability. In addition, the protein–protein interaction region showed a very high degree of identity (92%) within fragaceatoxins, but only 25% among all actinoporins examined, suggesting some degree of specificity at the species level. Our findings support the mechanism of evolutionary adaptation in actinoporins and reflect common pathways conducive to protein variability. View Full-Text
Keywords: actinoporins; protein variability; protein stability; protein structure; protein evolution actinoporins; protein variability; protein stability; protein structure; protein evolution

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Morante, K.; Bellomio, A.; Viguera, A.R.; González-Mañas, J.M.; Tsumoto, K.; Caaveiro, J.M.M. The Isolation of New Pore-Forming Toxins from the Sea Anemone Actinia fragacea Provides Insights into the Mechanisms of Actinoporin Evolution. Toxins 2019, 11, 401.

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