Ribosome inactivating proteins (RIPs) are toxins, which depurinate major RNA inhibiting protein synthesis1. The cleaved N-glycosidic bond corresponds to a specific adenine located in the sarcin/ricin loop, highly conserved in rRNAs from different species and essential for interaction with elongation factors. RIPs depurinate other polynucleotides as RNAs from different sources, DNA, poly(A), and even poly(ADP-ribosyl)ated proteins2. This action may lead to cell death by apoptosis or necrosis depending upon the level of damage. The three-dimensional structure of three type 1 RIPs, dianthin 303, bouganin and lychnin4, has been solved in the crystallographic research unit of Bologna. Their adenine polynucleotide glycosylase activity was also determined together with other known RIPs: PAP-R, momordin I, ricin A chain and saporin-S6. Saporin-S6 releases the highest number of adenine molecules from rat ribosomes, and poly(A), while its efficiency is similar to dianthin 30, bouganin and PAP-R on herring sperm DNA. Measurements of the protein synthesis inhibitory activity confirmed that saporin-S6 is the most active. The overall structure of the three studied proteins is similar to the other considered RIPs and the typical RIP fold is conserved. The superimposition of the Ca atoms highlights some differences in the N-terminal and C-terminal domains. Detailed structural and potential electrostatic analyses indicates that the efficiency of saporin-S6 on various polynucleotides may be ascribed to a negative electrostatic surface potential at the active site and several exposed positively charged residues in the region around that site. These two conditions, not present at the same time in others examined RIPs, may guarantee to saporin-S6 an efficient interaction with the substrates, characterized by a negatively charged backbone, and an efficient catalysis. 1. Endo Y, Tsurugi K (1987). J. Biol. Chem., 262:8128-8130. 2. Barbieri L, Brigotti M, Perocco P, Carnicelli D, Ciani M, Mercatali L, Stirpe F (2003). FEBS Lett., 538:178-182. 3. Fermani S, Falini G, Ripamonti A, Polito L, Stirpe F, Bolognesi A. (2005) J Struct Biol., 149:204-212. 4. Fermani S, Tosi G, Farini V, Polito L, Falini G, Ripamonti A, Roveri N, Barbieri L, Chambery A., Bolognesi A (2008) Proteins: Struct. Func. Bioinf., submitted.
S. Fermani, G. Tosi, V. Farini, L. Polito, G. Falini, A. Ripamonti, et al. (2008). Structure/funcion studies on type 1 ribosome inactivating proteins.. L'AQUILA : s.n.
Structure/funcion studies on type 1 ribosome inactivating proteins.
FERMANI, SIMONA;TOSI, GIOVANNA;FARINI, VALENTINA;POLITO, LETIZIA;FALINI, GIUSEPPE;RIPAMONTI, ALBERTO;BARBIERI, LUIGI;BOLOGNESI, ANDREA
2008
Abstract
Ribosome inactivating proteins (RIPs) are toxins, which depurinate major RNA inhibiting protein synthesis1. The cleaved N-glycosidic bond corresponds to a specific adenine located in the sarcin/ricin loop, highly conserved in rRNAs from different species and essential for interaction with elongation factors. RIPs depurinate other polynucleotides as RNAs from different sources, DNA, poly(A), and even poly(ADP-ribosyl)ated proteins2. This action may lead to cell death by apoptosis or necrosis depending upon the level of damage. The three-dimensional structure of three type 1 RIPs, dianthin 303, bouganin and lychnin4, has been solved in the crystallographic research unit of Bologna. Their adenine polynucleotide glycosylase activity was also determined together with other known RIPs: PAP-R, momordin I, ricin A chain and saporin-S6. Saporin-S6 releases the highest number of adenine molecules from rat ribosomes, and poly(A), while its efficiency is similar to dianthin 30, bouganin and PAP-R on herring sperm DNA. Measurements of the protein synthesis inhibitory activity confirmed that saporin-S6 is the most active. The overall structure of the three studied proteins is similar to the other considered RIPs and the typical RIP fold is conserved. The superimposition of the Ca atoms highlights some differences in the N-terminal and C-terminal domains. Detailed structural and potential electrostatic analyses indicates that the efficiency of saporin-S6 on various polynucleotides may be ascribed to a negative electrostatic surface potential at the active site and several exposed positively charged residues in the region around that site. These two conditions, not present at the same time in others examined RIPs, may guarantee to saporin-S6 an efficient interaction with the substrates, characterized by a negatively charged backbone, and an efficient catalysis. 1. Endo Y, Tsurugi K (1987). J. Biol. Chem., 262:8128-8130. 2. Barbieri L, Brigotti M, Perocco P, Carnicelli D, Ciani M, Mercatali L, Stirpe F (2003). FEBS Lett., 538:178-182. 3. Fermani S, Falini G, Ripamonti A, Polito L, Stirpe F, Bolognesi A. (2005) J Struct Biol., 149:204-212. 4. Fermani S, Tosi G, Farini V, Polito L, Falini G, Ripamonti A, Roveri N, Barbieri L, Chambery A., Bolognesi A (2008) Proteins: Struct. Func. Bioinf., submitted.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
