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A new class of enzyme acting on damaged ribosomes: ribosomal RNA apurinic site specific lyase found in wheat germ
Author(s) -
Ogasawara Tomio,
Sawasaki Tatsuya,
Morishita Ryo,
Ozawa Akihiko,
Madin Kairat,
Endo Yaeta
Publication year - 1999
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/18.22.6522
Subject(s) - biology , ribosome , wheat germ , ribosomal rna , ap site , lyase , enzyme , rna , biochemistry , genetics , microbiology and biotechnology , gene , endonuclease
A new enzyme, which we named ribosomal RNA apurinic site specific lyase (RALyase), is described. The protein was found in wheat embryos and has a molecular weight of 50 625 Da. The enzyme specifically cleaves the phosphodiester bond at the 3′ side of the apurinic site introduced by ribosome‐inactivating proteins into the sarcin/ricin domain of 28S rRNA. The 3′ and 5′ ends of wheat 28S rRNA at the cleavage site are 5′‐GUACG‐α‐hydroxy‐α,β‐unsaturated aldehyde and pGAGGA‐3′, demonstrating that the enzyme catalyzes a β‐elimination reaction. The substrate specificity of the enzyme is extremely high: it acts only at the apurinic site in the sarcin/ricin domain of intact ribosomes, not on deproteinized rRNA or DNA containing apurinic sites. The amino acid sequences of five endopeptidase LysC‐liberated peptides from the purified enzyme were determined and used to obtain a cDNA sequence. The open reading frame encodes a protein of 456 amino acids, and a homology search revealed a related rice protein. Similar enzyme activities were also found in other plants that express ribosome‐inactivating proteins. We believe that RALyase is part of a complex self‐defense mechanism.