Ribosome Inactivating Proteins from Rosaceae

Pierre Rougé,Chenjing Shang,Els Van Damme

doi:10.3390/molecules21081105

Abstract

Ribosome-inactivating proteins (RIPs) are widespread among higher plants of different taxonomic orders. In this study, we report on the RIP sequences found in the genome/transcriptome of several important Rosaceae species, including many economically important edible fruits such as apple, pear, peach, apricot, and strawberry. All RIP domains from Rosaceae share high sequence similarity with conserved residues in the catalytic site and the carbohydrate binding sites. The genomes of Malus domestica and Pyrus communis contain both type 1 and type 2 RIP sequences, whereas for Prunus mume, Prunus persica, Pyrus bretschneideri, and Pyrus communis a complex set of type 1 RIP sequences was retrieved. Heterologous expression and purification of the type 1 as well as the type 2 RIP from apple allowed to characterize the biological activity of the proteins. Both RIPs from Malus domestica can inhibit protein synthesis. Furthermore, molecular modelling suggests that RIPs from Rosaceae possess three-dimensional structures that are highly similar to the model proteins and can bind to RIP substrates. Screening of the recombinant type 2 RIP from apple on a glycan array revealed that this type 2 RIP interacts with terminal sialic acid residues. Our data suggest that the RIPs from Rosaceae are biologically active proteins.

Highlights

Ribosome-inactivating proteins (RIPs) are a large family of enzymes (EC.3.2.2.22) comprising an rRNA N-glycosylase domain that is capable of catalytically inactivating ribosomes through the removal of a specific adenine residue from a highly conserved α-sarcin/ricin loop within the large rRNA [1]
Plant RIPs are classically subdivided in two major groups: Type 1 RIPs consist of a single protein domain with rRNA N-glycosylase activity (RIP domain), whereas type 2 RIPs are chimeric proteins built up of an N-terminal rRNA N-glycosylase domain (RIP domain) fused to a C-terminal carbohydrate binding domain
A total of 16 genes encoding putative type 1 RIP genes and two genes encoding putative type 2 RIP genes were identified in Rosaceae species including Malus domestica, Prunus mume, Prunus persica

Summary

Introduction

Ribosome-inactivating proteins (RIPs) are a large family of enzymes (EC.3.2.2.22) comprising an rRNA N-glycosylase domain that is capable of catalytically inactivating ribosomes through the removal of a specific adenine residue from a highly conserved α-sarcin/ricin loop within the large rRNA [1]. Though RIPs have first been detected and characterized from plants, RIPs have been isolated and characterized from bacteria and fungi, and more recently RIP sequences have been reported in insects [2]. Apart from the shiga and shiga-like toxins from bacteria [3] and a few fungal RIPs from mushrooms [4], virtually all research concentrated on RIPs are from flowering plants. Plant RIPs are classically subdivided in two major groups: Type 1 RIPs consist of a single protein domain with rRNA N-glycosylase activity (RIP domain), whereas type 2 RIPs are chimeric proteins built up of an N-terminal rRNA N-glycosylase domain (RIP domain) fused to a C-terminal carbohydrate binding domain (lectin domain). RIPs are widely distributed in the plant kingdom and RIP sequences have been reported for at least 71 monocotyledonous and dicotyledonous species within the Angiospermae [5].

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