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Involvement of loop 5 lysine residues and the N-terminal β-hairpin of the ribotoxin hirsutellin A on its insecticidal activity



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Olombrada, Miriam and García Ortega, Lucía and Lacadena, Javier and Oñaderra, Mercedes and Gavilanes, José G. and Martínez del Pozo, Álvaro (2016) Involvement of loop 5 lysine residues and the N-terminal β-hairpin of the ribotoxin hirsutellin A on its insecticidal activity. Biological chemistry, 397 (2). pp. 135-145. ISSN 1437-4315 (Online), 1431-6730 (print)

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Official URL: http://www.degruyter.com/view/j/bchm.2016.397.issue-2/hsz-2015-0261/hsz-2015-0261.xml


Ribotoxins are cytotoxic members of the family of fungal extracellular ribonucleases best represented by RNase T1. They share a high degree of sequence identity and a common structural fold, including the geometric arrangement of their active sites. However, ribotoxins are larger,with a well-defined N-terminal β-hairpin, and display longer and positively charged unstructured loops. These structural differences account for their cytotoxic properties.Unexpectedly, the discovery of hirsutellin A (HtA), a ribotoxin produced by the invertebrate pathogen Hirsutella thompsonii, showed how it was possible to accommodate these features into a shorter amino acid sequence. Examination of HtA N-terminal β-hairpin reveals differences in terms of length, charge, and spatial distribution. Consequently,four different HtA mutants were prepared and characterized. One of them was the result of deleting this hairpin [Δ(8-15)] while the other three affected single Lys residues in its close spatial proximity (K115E, K118E, and K123E). The results obtained support the general conclusion that HtA active site would show a high degree of plasticity,being able to accommodate electrostatic and structural changes not suitable for the other previously known larger ribotoxins, as the variants described here only presented small differences in terms of ribonucleolytic activity and cytotoxicity against cultured insect cells.

Item Type:Article
Uncontrolled Keywords:hirsutellin A; insecticidal; ribonucleases; ribotoxins; rRNA
Subjects:Medical sciences > Biology > Biochemistry
ID Code:38199
Deposited On:21 Jun 2016 10:08
Last Modified:12 Jun 2017 10:22

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