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Characterization of Pokeweed Antiviral Protein's interaction with eukaryotic initiation factors and an S/R loop oligo
Author(s) -
Friedland Diana Elaine,
Goss Dixie J.,
DeGrazia Jeannine,
Baldwin Amy E.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.998.4
Subject(s) - rna , ribosome , binding site , biology , ribosome inactivating protein , nucleotide , biochemistry , ricin , gtp' , rna binding protein , microbiology and biotechnology , chemistry , enzyme , gene , toxin
Plant viruses have numerous invasion strategies thus plants have devised ways to continuously defend themselves against pathogenic attack. Ribosome‐inactivating proteins (RIPs) are naturally occurring cytotoxic N ‐glycosidase agents and are found in numerous species. They inhibit protein synthesis by depurinating A4324 on the conserved sarcin/ricin loop (SRL) of the 28S rRNA. Pokeweed Antiviral Protein (PAP) is a type I RIP that has long been recognized as an antiviral agent. It is also able to inhibit infection without loss of host cell translation. Here we report in vitro fluorescence studies of PAP‐eIFiso4G binding revealing an interaction with a Kd of approximately 100 nM. This interaction enhances the cap binding affinity of PAP 3‐fold. Our experiments have shown that PAP binds to cap with a similar affinity to that of the wheat germ cap binding protein eIFiso4E. ATP and GTP compete with cap for PAP binding; both nucleotides and the cap analog show little salt dependence in binding, suggesting that the interactions are specific for these nucleotides. Binding to an oligonucleotide that contains the S/R sequence was slightly weaker than cap binding. We have also determined that PAP directly interacts with eIFiso4E. The biological significance of PAP‐cap binding remains unclear, however this may serve as a means to target RNA or, since ATP binds to the same site, this may be a protective mechanism for host cell capped RNA. The interaction with initiation factors suggests that additional proteins may aid PAP in accessing particular RNA and distinguishing structural elements of the RNA. This work was supported in part by a Research Opportunity Award (NSF MCB 0413982 and a CUNY Collaborative Incentive Research Grant 80209‐07‐12).