Some ribosome-inactivating proteins depurinate ribosomal RNA at multiple sites

Abstract

Saporin-S6, a ribosome-inactivating protein (RIP) from Saponaria officinalis released more than 1 mol of adenine/mol of ribosomes from house fly (Musca domestica) larvae and from rat liver. The release of adenine from rat liver ribosomes by several RIPs (plant enzymes with RNA N-glycosidase activity) was examined. Saporins, pokeweed antiviral protein from roots of Phytolacca americana (PAP-R), and trichokirin from Trichosanthes kirilowii seeds depurinated rat liver ribosomes at more than one site. Up to 33 mol of adenine were released from 1 mol of ribosomes. This property is not common to all RIPS. INTRODUCI ONRibosome-inactivating proteins (RIPs) from plants (reviewed in [11), of either type I (single-chain proteins) or type 2 (twochain proteins, ricin and related toxins), damage ribosomes from eukaryotes and, at higher concentrations, ribosomes from prokaryotes 12-4J. They are RNA N-glycosidases which depurinate the major ribosomal RNA at a position corresponding to adenine-4324 of rat liver 28 S rRNA [5,6]. This site of action is a highly conserved loop-and-stem structure, and the conditions necessary for its identification by ricin have been determined by Endo and co-workers [7]. This is the only known site of action of RIPs on eukaryotic ribosomes, although ricin [7] and Mirabilis antiviral protein [3] also depurinated naked 16 S Escherichia coli rRNA at another site, A-1014. We report here that saporins (RIPs from seeds, leaves and roots of Saponaria officinalis), pokeweed antiviral protein from Phytolacca americana roots (PAP-R), and trichokirin from Trichosanthes kirilowii seeds depurinate rat liver ribosomes more extensively than do other known RIPs.

A systemic antiviral resistance‐inducing protein isolated from Clerodendrum inerme Gaertn. is a polynucleotide:adenosine glycosidase (ribosome‐inactivating protein)

“…These effects are catalytic, as shown by molar ratio less than 1 between RIP present in the reaction mixture and adenine released. From the characteristics of their enzymatic activity, RIPs appear to be a non-homogeneous class of enzymes, in that (i) some release one, and some more than one adenine residues per ribosome [14], (ii) some are more active on poly(A) than on RNA [15,16] and (iii) have variable activity on RNA and on DNA (unpublished results). CIP-29 releases only one adenine residue from rat liver ribosomes, is not particularly active on poly(A), but is very active on DNA, more than any RIP assayed so far under the same experimental conditions.…”

“…RIPs were found to be peculiar N-glycosidases, and to remove a single adenine from a precise position in rRNA (A 4324 in the case of rat liver ribosomes) (review in [13]). More recently, however, it was reported that some, but not all, RIPs remove more than one adenine residue per ribosome [14], and that saporins [15,16] and other RIPs ( [12]; unpublished results by Barbieri et al) remove adenine from RNA other than rRNA and also from DNA. Consistently, ricin removes 2'-deoxyadenine from a synthetic dodecanucleotide with a GdA-GA loop, actually at a faster rate than it removes adenine from a similar dodecanucleotide with a GAGA loop [17].…”

Photochemically stimulated drug delivery increases the cytotoxicity and specificity of EGF–saporin

“…These RIPs exerts N-glycosidase activity against the 28S RNA of the 60S ribosomal subunit, causing arrest of the protein synthesis which consequently induces cell death (Endo et al 1987, Barbieri et al 1992. RIPs can mainly be divided into 2 groups, type I and type II (Barbieri et al 1993, Nielsen & Boston 2001.…”

The N-Glycosidase Activity of the Ribosome-inactivating Protein ME1 Targets Single-stranded Regions of Nucleic Acids Independent of Sequence or Structural Motifs

“…For instance, it has been shown that several RIPs can release adenine from multiple sites in rRNA (5). Furthermore, saporin-L1 can release adenine residues from a variety of nucleic acid substrates, including poly(A), mRNA, tRNA, and DNA (6,7).…”