Correlation between the activities of five ribosome‐inactivating proteins in depurination of tobacco ribosomes and inhibition of tobacco mosaic virus infection

Abstract

SummaryThe rRNA depurination activities of five ribosomeInactivating proteins (RIPs) were compared in vitro using yeast and tobacco leaf ribosomee as substrates. All of the RIPs (pokeweed antlvirel protein (PAP), dianthin 32, trltin, barley RIP end ricin A-chain) were active on yeast ribosomes. PAP and dlanthin 32 were highly active and ricin A-chain weekly active on tobacco ribosomes, whereas trltin and barley RIP were inactive. PAP and dlanthin 32 were highly effective in inhibiting the formation of local lesions caused by tobacco mosaic virus (TMV) on tobacco leaves, whereas tritin, barley RIP and ricin A-chain were ineffective. The apparent anomaly between the in vitro rRNA depurinatlon activity, but lack of antiviral activity of ricin A-chain was further Investigated by assaying for rRNA depurinstion in situ following the topical application of the RIP to leaves. No activity was detected, a finding consistent with the apparent lack of antlviral activity of this RIP. Thus, it is concluded that there is a positive correlation between RIP-catalyeed depurination of tobacco ribosomes and antlviral activity which gives strong support to the hypothesis that the antiviral activity of RIPs works through ribosome inactivation.

A Ribosome–Inactivating Protein fromAmaranthus viridis

“…Generally RIPs from various plants have basic properties, so we used a basic buffer (10 mM Tris buffer, pH 9.0) to reduce the amount of contaminating proteins. Fractions from the S-sepharose column that showed inhibition of tobacco mosaic virus (TMV) infecton on leaves of Nicotiana glutinosa 9 ) were put on the Mono S column. From the Mono S column ( Fig.…”

Structural Insights into the Neutralization Mechanism of Monoclonal Antibody 6C2 against Ricin

“…However, several studies had established the importance of the ribosomal proteins in facilitating the depurination activity and ribosome specificity of ricin (34,35). Thus, targeting ricin accurately to the ribosome was a prerequisite for the RNA N-glycosidase activity.…”

Pathogen-Derived Resistance Against Plant Viruses: Postscript and Prospects

“…These strategies have involved antibody (Tavladoraki et al, 1993) cytotoxin or inhibitor protein genes, often designed to be activated only when a uniquely viral event occurs e.g., dsRNA mediated activation of the 2,5-A (interferon-like) pathway (Truve et al, 1993). Strategies involved in the expression of wound-induced pathogenesis-related proteins, or ribsomeinactiviating proteins (Taylor et al, 1994) such as ricin, pokeweed antiviral protein (Lodge et al, 1993), or diphtheria toxin. The prospect of widespread environmental releases of crop plants expressing some (or any) of these (latent) cytotoxic genes will doubtless call for careful review and stringent risk assessments to be made.…”