Ribosome-Inactivating Proteins

Dear Colleagues,

Ribosome-inactivating proteins (RIPs) are ribosomal RNA N-glycosylases (EC 3.2.2.22), isolated mainly from angiosperms and also from some bacteria and fungi, which catalyse the hydrolysis of the N-glycosidic bond of the second adenosine of the GAGA tetraloop in the sarcin ricin loop (SRL) of the large subunit ribosomal RNA. The SRL is part of the GTPase-associated centre (GAC), which is the landing platform for the translational GTPases (trGTPases), such as the prokaryotic elongation factors EF-Tu and EF-G, and their eukaryotic homologues eEF1A and eEF2. Depurination of the SRL causes irreversible inactivation of ribosomes, leading to cell death, mainly by apoptosis. Although RIPs were initially studied as inhibitors of mammalian ribosomes, they can also inactivate ribosomes from other animals and fungi and, in some cases, ribosomes from bacteria and plants.

In addition, RIPs can exhibit other enzymatic activities, the most relevant being their adenine polynucleotide glycosylase activity in all types of nucleic acids (including viral RNA or DNA).

It has been proposed that these proteins could play an important role in plant defence against viruses, fungi and insects.

RIPs have been classified into two types according to the presence (type 2) or absence (type 1) of a lectin chain (B chain). The presence of the B chain can convert type 2 RIPs into potent toxins, such as ricin or abrin. However, despite the absence of the B chain, type 1 RIPs (such as saporin or trichosantin), in higher concentrations, are also capable of entering cells and exhibiting toxicity to cells and animals.

Due to their diverse activities, RIPs are good candidates for the development of selective antiviral and anticancer agents such as conjugates, immunotoxins, engineered proteins, and nanocapsules. In agriculture, RIPs have been shown to increase resistance to viruses, fungi, and insects in transgenic plants.

This Topical Collection accepts submissions related to the topics described above.

Prof. Dr. José Miguel Ferreras
Prof. Dr. Lucía Citores
Prof. Dr. Rosario Iglesias
Topical Editors

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