Self-homodimerization of an actinoporin by disulfide bridging reveals implications for their structure and pore formation

• Published in: Scientific reports Vol. 8; no. 1; pp. 6614 - 18
• Main Authors: Valle, Aisel, Pérez-Socas, Luis Benito, Canet, Liem, Hervis, Yadira de la Patria, de Armas-Guitart, German, Martins-de-Sa, Diogo, Lima, Jônatas Cunha Barbosa, Souza, Adolfo Carlos Barros, Barbosa, João Alexandre Ribeiro Gonçalves, de Freitas, Sonia Maria, Pazos, Isabel Fabiola
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26-04-2018; Nature Publishing Group
• Subjects: 631/45/535/1267; 631/45/612/1237; 631/57/2272/2273; 82/16; 82/29; 82/58; 82/80; 82/83; Binding sites; Circular dichroism; Dimerization; Disulfide bonds; Humanities and Social Sciences; Light scattering; Monomers; multidisciplinary; Science; Science (multidisciplinary); Spectroscopy; Ultracentrifugation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-24688-2

The Trp111 to Cys mutant of sticholysin I, an actinoporin from
Stichodactyla helianthus
sea anemone, forms a homodimer via a disulfide bridge. The purified dimer is 193 times less hemolytic than the monomer. Ultracentrifugation, dynamic light scattering and size-exclusion chromatography demonstrate that monomers and dimers are the only independent oligomeric states encountered. Indeed, circular dichroism and fluorescence spectroscopies showed that Trp/Tyr residues participate in homodimerization and that the dimer is less thermostable than the monomer. A homodimer three-dimensional model was constructed and indicates that Trp147/Tyr137 are at the homodimer interface. Spectroscopy results validated the 3D-model and assigned 85° to the disulfide bridge dihedral angle responsible for dimerization. The homodimer model suggests that alterations in the membrane/carbohydrate-binding sites in one of the monomers, as result of dimerization, could explain the decrease in the homodimer ability to form pores.