Comparison of Enzymatic Activities of Pokeweed Antiviral Protein (PAP) Isoforms toward RNA from the Tobacco Etch Virus

Abstract

Plants produce ribosome‐inactivating proteins (RIPs) phytotoxins that serve an important role in plants’ defense mechanisms against pathogenic invaders. RIPs are RNA N‐glycosidases that inhibit protein synthesis of a host cell through depurination of highly conserved sarcin/ricin loop of large ribosomal RNA. After synthesized inside the cells, RIPs are exocytosed and stored within extracellular spaces. Once a pathogenic attack occurs, RIPs gain access into the cell, alongside with a pathogen. Lesions within depurinated ribosomal RNA, produced by enzymatic activity of RIPs, avert the translocation step of protein synthesis. As a result, ribosome stalls.. The common pokeweed plant, Phytolacca americana, produces pokeweed antiviral protein (PAP), a type 1 RIP. PAP had been interacts directly with viral RNAs, depurinates them directly, and does so without substantial damage to the host ribosoms. PAP lowers the infectivity of many plant and animal viruses, including HIV‐1, poliovirus, and influenza. Nine known isoforms of PAP are produced in different parts of the plant; these vary during seasonal development. The mechanism of PAP‐viral RNA selectivity is not well known, and antiviral activity among different PAP isoforms varies. The focus of this study is to gain a deeper understanding into PAP‐RNA selectivity mechanism, and examine which isoforms of PAP exhibit the greatest activity toward tobacco etch virus (TEV) RNA. This knowledge will further be used in the development of efficient antiviral treatments.Support or Funding InformationTitle V, HSI‐STEM and MSEIP programs within the U.S. Department of Education; the PAESMEM program through the National Science Foundation; and New York State's Graduate Research and Technology Initiative. Professional Stuff Congress of the City University of New York (PSC‐CUNY), Cycle 44 Award.