title: Involvement of loops 2 and 3 of α-sarcin on its ribotoxic activity.
abstract: Ribotoxins are a family of fungal ribosome-inactivating proteins displaying highly specific ribonucleolytic activity against the sarcin/ricin loop (SRL) of the larger rRNA, with α-sarcin as its best-characterized member. Their toxicity arises from the combination of this activity with their ability to cross cell membranes. The involvement of α-sarcin's loops 2 and 3 in SRL and ribosomal proteins recognition, as well as in the ribotoxin-lipid interactions involving cell penetration, has been suggested some time ago. In the work presented now different mutants have been prepared in order to study the role of these loops in their ribonucleolytic and lipid-interacting properties. The results obtained confirm that loop 3 residues Lys 111, 112, and 114 are key actors of the specific recognition of the SRL. In addition, it is also shown that Lys 114 and Tyr 48 conform a network of interactions which is essential for the catalysis. Lipid-interaction studies show that this Lys-rich region is indeed involved in the phospholipids recognition needed to cross cell membranes. Loop 2 is shown to be responsible for the conformational change which exposes the region establishing hydrophobic interactions with the membrane inner leaflets and eases penetration of ribotoxins target cells.
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Castaño-Rodríguez
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Miriam
authors.initials: M
authors.lastname: Olombrada
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Angélica
authors.initials: A
authors.lastname: Partida-Hanon
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Lacadena
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Oñaderra
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain. Electronic address: ppgf@bbm1.ucm.es.
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain.
authors.forename: Lucía
authors.initials: L
authors.lastname: García-Ortega
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Facultades de Química y Biología, Universidad Complutense, 28040 Madrid, Spain. Electronic address: alvaromp@quim.ucm.es.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Martínez-Del-Pozo
mesh_terms: D065966:Absorption, Physicochemical; D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D002460:Cell Line; D002942:Circular Dichroism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D004722:Endoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity*; D004926:Escherichia coli; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009841:Oligonucleotides / Q000235:genetics; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011500:Protein Synthesis Inhibitors / Q000633:toxicity*; D012270:Ribosomes / Q000187:drug effects*; D016415:Sequence Alignment; D013053:Spectrophotometry; D018411:Spodoptera
chemical_list: D018076:DNA, Complementary; D005656:Fungal Proteins; D009841:Oligonucleotides; D010743:Phospholipids; D011500:Protein Synthesis Inhibitors; C014801:alpha-sarcin; D004722:Endoribonucleases
keywords: Cation-π interaction; Lys-rich region; Ribotoxin; SRL