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Minimized natural versions of fungal ribotoxins show improved active site plasticity

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Maestro-López, Moisés and Olombrada, Miriam and García Ortega, Lucía and Serrano González, Daniel and Lacadena, Javier and Oñaderra, Mercedes and Gavilanes, José G. and Martínez del Pozo, Álvaro (2017) Minimized natural versions of fungal ribotoxins show improved active site plasticity. Archives of Biochemistry and Biophysics . ISSN 1096-0384 (Online)

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Official URL: http://www.sciencedirect.com/science/article/pii/S0003986117300346



Abstract

Fungal ribotoxins are highly specific extracellular RNases which cleave a single phosphodiester bond at the ribosomal sarcin-ricin loop, inhibiting protein biosynthesis by interfering with elongation factors. Most ribotoxins show high degree of conservation, with similar sizes and amino acid sequence identities above 85%. Only two exceptions are known: Hirsutellin A and anisoplin, produced by the entomopathogenic fungi Hirsutella thompsonii and Metarhizium anisopliae, respectively. Both proteins are similar but smaller than the other known ribotoxins (130 vs 150 amino acids), displaying only about 25% sequence identity with them. They can be considered minimized natural versions of their larger counterparts, best represented by α-sarcin. The conserved α-sarcin active site residue Tyr48 has been replaced by the geometrically equivalent Asp, present in the minimized ribotoxins, to produce and characterize the corresponding mutant. As a control, the inverse anisoplin mutant (D43Y) has been also studied. The results show how the smaller versions of ribotoxins represent an optimum compromise among conformational freedom, stability, specificity, and active-site plasticity which allow these toxic proteins to accommodate the characteristic abilities of ribotoxins into a shorter amino acid sequence and more stable structure of intermediate size between that of other nontoxic fungal RNases and previously known larger ribotoxins.


Item Type:Article
Uncontrolled Keywords:RNases; Insecticidal; Sarcin; Hirsutellin; Anisoplin
Subjects:Sciences > Chemistry > Molecular biology
Sciences > Chemistry > Biochemistry
ID Code:41812
Deposited On:14 Mar 2017 12:20
Last Modified:07 Feb 2018 11:36

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