title: N-terminal deletion affects catalytic activity of saporin toxin.
abstract: Single-chain ribosome inactivating proteins (RIPs) are cytotoxic components of macromolecular pharmaceutics for immunotherapy of cancer and other human diseases. Saporin belongs to a family of single-chain RIPs sharing sequence and structure homology. In a preliminary attempt to define an active saporin polypeptide of minimum size we have generated proteins with deletions at the N-terminus and at the C-terminus. An N-terminal (sapDelta1-20) deletion mutant of saporin displayed defective catalytic activity, drastically reduced cytotoxicity but increased ability to interact with liposomes inducing their permeabilization at low pH. A C-terminal (sapDelta239-253) deletion mutant showed instead a moderate reduction in cytotoxic activity. A substantial alteration of secondary structure was evidenced by Fourier transformed infrared spectroscopy (FTIR) in the sapDelta1-20 mutant. It can be hypothesized that the defective functions of sapDelta1-20 are due to alterations of its spatial configuration.
authors.affiliation: Department of Pathology, Section of Immunology, University of Verona, Policlinico G.B. Rossi, Largo L.A. Scuro 10. I-37134 Verona, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Bonini
authors.forename: Roberta
authors.initials: R
authors.lastname: Traini
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Comper
authors.forename: Giulio
authors.initials: G
authors.lastname: Fracasso
authors.forename: Rossella
authors.initials: R
authors.lastname: Tomazzolli
authors.forename: Mauro
authors.initials: M
authors.lastname: Dalla Serra
authors.forename: Marco
authors.initials: M
authors.lastname: Colombatti
mesh_terms: D002384:Catalysis; D045744:Cell Line, Tumor; D003124:Colorimetry; D017353:Gene Deletion; D006801:Humans; D000922:Immunotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D008567:Membranes, Artificial; D009154:Mutation / Q000235:genetics; D014176:Protein Biosynthesis / Q000187:drug effects; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity; D017433:Protein Structure, Secondary; D013379:Substrate Specificity
chemical_list: D000922:Immunotoxins; D008567:Membranes, Artificial; D020033:Protein Isoforms