title: The sea anemone actinoporin (Arg-Gly-Asp) conserved motif is involved in maintaining the competent oligomerization state of these pore-forming toxins.
abstract: Sea anemone actinoporins constitute an optimum model to investigate mechanisms of membrane pore formation. All actinoporins of known structure show a general fold of a β-sandwich motif flanked by two α-helices. The crucial structure for pore formation seems to be the helix located at the N-terminal end. The role of several other protein regions in membrane attachment is also well established. However, not much is known about the protein residues involved in the oligomerization required for pore formation. Previous detailed analysis of the soluble three-dimensional structures of different wild-type and mutant actinoporins from Stychodactyla helianthus suggested residues which could be involved in this oligomerization. One of these stretches contains a conserved sequence compatible with an integrin-binding RGD motif. The results presented now deal with mutants affecting this motif in the well-characterized actinoporin sticholysin II. Small modifications along this three-residue sequence had profound effects on its solubility. Just a single methyl group yielded an RAD mutant version with a highly diminished haemolytic activity and altered oligomerization behaviour. The results obtained are discussed in terms of a key role for the RGD motif in maintaining the actinoporins' pore-competent state of protein oligomerization.
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain.
authors.forename: Sara
authors.initials: S
authors.lastname: García-Linares
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain.
authors.forename: Ryan
authors.initials: R
authors.lastname: Richmond
authors.affiliation: Instituto de Química-Física Rocasolano, Madrid, Spain.
authors.forename: María F
authors.initials: MF
authors.lastname: García-Mayoral
authors.affiliation: Instituto de Química-Física Rocasolano, Madrid, Spain.
authors.forename: Noemí
authors.initials: N
authors.lastname: Bustamante
authors.affiliation: Instituto de Química-Física Rocasolano, Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Bruix
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain.
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, Madrid, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Martínez-Del-Pozo
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D003064:Cnidarian Venoms / Q000737:chemistry* / Q000235:genetics* / Q000633:toxicity; D017124:Conserved Sequence; D006461:Hemolysis / Q000187:drug effects; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry* / Q000235:genetics* / Q000633:toxicity; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D012615:Sea Anemones / Q000737:chemistry / Q000235:genetics
chemical_list: D003064:Cnidarian Venoms; D052899:Pore Forming Cytotoxic Proteins; C404794:sticholysin II
keywords: actinoporin; equinatoxin; haemolysis; integrin; pore formation; sticholysin