1;Editors;6 2;Preface;8 3;Contents;10 4;Evolution of Plant Ribosome-Inactivating Proteins;12 4.1;1 Introduction;12 4.2;2 General Overview of the Taxonomic Distribution of A and B Domains within the Viridiplantae;13 4.3;3 Overview of the Taxonomic Distribution of A and B Domains within the Magnoliophyta (Flowering Plants);15 4.3.1;3.1 ``Classical´´ Type 2 RIPs (AB proteins);15 4.3.2;3.2 Other Proteins with Ricin- Domains;16 4.4;4 Molecular Evolution of Type 2 RIPs;16 4.4.1;4.1 General Observations Concerning the Taxonomic Distribution of Type 2 RIPs and the Occurrence of Multiple Paralogs;16 4.4.2;4.2 Overall Phylogeny of Type 2 RIPs;17 4.4.3;4.3 Special Evolutionary Events: Gene Amplification and Generation of Type A and Type B Proteins from Genuine Type 2 RIPs;19 4.4.4;4.4 What is the Origin of Type 2 RIP Genes?;22 4.4.4.1;4.4.1 Origin of the B-hain;22 4.4.4.2;4.4.2 Origin of the A-hain;23 4.5;5 Molecular Evolution of Type 1 RIPs;23 4.5.1;5.1 Dicots and Monocots Other Than Poaceae;24 4.5.2;5.2 Poaceae Type 1 RIPs;27 4.5.2.1;5.2.1 O. sativa;27 4.5.2.2;5.2.2 Andropogoneae: Z. mays and Sorghum bicolor;28 4.5.2.3;5.2.3 Pooideae;29 4.5.2.4;5.2.4 Relationships between the RIPs from Poaceae and Other Seed Plants;29 4.6;6 What is the Relationship between Plant and Bacterial RIPs?;31 4.7;7 Chimeric RIPs Other Than Type 2 RIPs;31 4.7.1;7.1 JIP60 and Other Type AC Chimeric RIPs;31 4.7.2;7.2 Chimeric RIP with a C-erminal D Domain;34 4.8;8 Conclusions;34 4.9;References;36 5;RNA N-Glycosidase Activity of Ribosome-Inactivating Proteins;38 5.1;1 Introduction;38 5.2;2 Ricin as an RNA N-lycosidase;39 5.2.1;2.1 28S rRNA as the Target of Modification by Ricin and Other RIPs;39 5.2.2;2.2 RNA N-lycosidase Activity of Ricin A-hain;41 5.2.3;2.3 Other RIPs;42 5.2.4;2.4 Major Role of RNA in Protein Synthesis;42 5.3;3 Ribosomal Mechanisms Involving the Sarcin-icin Domain;43 5.3.1;3.1 Eukaryotic Translation Can Be Inhibited Strongly by Dysfunction of a Small Fraction of the Ribosome Population;43 5.3.2;3.2 Difference in the Modes of Action between a-arcin and Ricin;43 5.3.3;3.3 Substrate Specificity;44 5.3.4;3.4 Structure of the SRL;44 5.4;4 Ribosomal RNA Apurinic Site-pecific Lyase: Intrinsic Stability of the Ribosome;46 5.5;References;48 6;Enzymatic Activities of Ribosome-Inactivating Proteins;51 6.1;1 Introduction;51 6.2;2 Action of RIPs on Ribosomes and rRNA;52 6.2.1;2.1 Site of Modification by RIPs;52 6.2.2;2.2 Structural Requirements in Ribosomal RNA for RIP Action;53 6.3;3 Polynucleotide:Adenosine Glycosidase Activity;56 6.3.1;3.1 5 Cap-ndependent Activity;56 6.3.2;3.2 5 Cap-ependent Activity;57 6.4;4 DNA Lyase;59 6.5;5 Bifunctional Enzymes with RIP Activity in Which the Non-IP Activity Acts on Non-ucleic Acid Substrates;59 6.5.1;5.1 Lipase;59 6.5.2;5.2 Chitinase;60 6.5.3;5.3 Superoxide Dismutase;60 6.6;6 Conclusions;61 6.7;References;62 7;Type I Ribosome-Inactivating Proteins from Saponaria officinalis;65 7.1;1 Introduction;65 7.2;2 Saporin Multigene Family and Saporin Isoforms;66 7.3;3 Saporin Biochemical Features;68 7.3.1;3.1 Saporin Structure;68 7.3.2;3.2 Saporin Catalytic Activity;71 7.3.3;3.3 Residues Important for the Catalytic Activity;72 7.3.4;3.4 Interaction with the Ribosome;73 7.3.5;3.5 Saporin Inhibitors;74 7.4;4 Saporin Trafficking and Toxicity in Eukaryotic Cells;75 7.4.1;4.1 Subcellular Distribution of Saporin Isoforms in Soapwort Tissues;75 7.4.2;4.2 Saporin Biosynthesis and Role in Planta;76 7.4.3;4.3 Intoxication Pathways in Mammalian Cells;77 7.5;5 Heterologous Expression of Saporin and Saporin Fusion Toxins;80 7.6;6 Conclusions and Perspectives;82 7.7;References;82 8;Type 1 Ribosome-Inactivating Proteins from the Ombú Tree (Phytolacca dioica L.);89 8.1;1 Introduction;89 8.2;2 RIPs from P. dioica L.;90 8.2.1;2.1 Isolation of RIPs from Seeds and Leaves of P. dioica;92 8.2.2;2.2 Basic Characteristics of RIPs from Seeds and Leaves of P. dioica;92 8.2.3;2.3 Differential Seasonal and Age Expression in Leaves;97 8.2.4;2.4 Cellular L