title: Sequence comparison and phylogenetic analysis by the Maximum Likelihood method of ribosome-inactivating proteins from angiosperms.
abstract: Ribosome-inactivating proteins (RIPs) from angiosperms are rRNA N-glycosidases that have been proposed as defence proteins against virus and fungi. They have been classified as type 1 RIPs, consisting of single-chain proteins, and type 2 RIPs, consisting of an A chain with RIP properties covalently linked to a B chain with lectin properties. In this work we have carried out a broad search of RIP sequence data banks from angiosperms in order to study their main structural characteristics and phylogenetic evolution. The comparison of the sequences revealed the presence, outside of the active site, of a novel structure that might be involved in the internal protein dynamics linked to enzyme catalysis. Also the B-chains presented another conserved structure that might function either supporting the beta-trefoil structure or in the communication between both sugar-binding sites. A systematic phylogenetic analysis of RIP sequences revealed that the most primitive type 1 RIPs were similar to that of the actual monocots (Poaceae and Asparagaceae). The primitive RIPs evolved to the dicot type 1 related RIPs (like those from Caryophyllales, Lamiales and Euphorbiales). The gene of a type 1 RIP related with the actual Euphorbiaceae type 1 RIPs fused with a double beta trefoil lectin gene similar to the actual Cucurbitaceae lectins to generate the type 2 RIPs and finally this gene underwent deletions rendering either type 1 RIPs (like those from Cucurbitaceae, Rosaceae and Iridaceae) or lectins without A chain (like those from Adoxaceae).
authors.affiliation: Department of Environmental, Biological and Pharmaceutical Sciences and Technologies, Second University of Naples, 81100, Caserta, Italy.
authors.forename: Antimo
authors.initials: A
authors.lastname: Di Maro
authors.forename: Lucía
authors.initials: L
authors.lastname: Citores
authors.forename: Rosita
authors.initials: R
authors.lastname: Russo
authors.forename: Rosario
authors.initials: R
authors.lastname: Iglesias
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Ferreras
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D016013:Likelihood Functions; D019684:Magnoliopsida / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D017434:Protein Structure, Tertiary; D054788:Ribosome Inactivating Proteins / Q000737:chemistry* / Q000235:genetics; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
chemical_list: D010940:Plant Proteins; D054788:Ribosome Inactivating Proteins