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Faculty Sponsor

Dr. George Mourad

Department/Program

Department of Biology

University Affiliation

Indiana University – Purdue University Fort Wayne

IPFW Sigma Xi (Scientific Research Honor Society) Student Research Competition

Best Undergraduate Student Poster Presentation

Abstract

Nucleobases and their precursors are vital organic molecules in all living cells due to their role in nucleic acid biochemistry, sugar metabolism, as well as serving as energy molecules. In plants, the salvage and catabolism of nucleobases requires an intricate membrane transport mechanism that ensures their movement between cells and also within cells between the organelles and cytoplasm. One of several nucleobase transporter membrane families that have been identified is the Nucleobase Cation Symporter 1 (NCS1). In this report the specific nucleobase substrates transported by the sole NCS1 protein of corn (Zea mays), ZmNCS1, and by its relative grass Setaria viridis, SvNCS1, are identified. The genes encoding ZmNCS1 and SvNCS were PCR-cloned then spliced into a yeast expression vector. The yeast vectors containing the plant genes were transformed into yeast cells lacking their native NCS1. Such yeast cells were then used to identify the substrate specificity of the expressed plant NCS1 proteins using three approaches. First, by growing on media containing toxic structural analogs of various nucleobases. Second, by growing on medium where nucleobases are the sole nitrogen source. Third, by assaying for the uptake of a panel of radiolabeled nucleobases from the growth medium into the cells. In addition, homologous and heterologous competition between radiolabelled substrates and an array of non-radioactive nucleobases revealed the kinetic properties of uptake for both plant NCS1 proteins. The results revealed that ZmNCS1 and SvNCS1 proteins have novel functions, in that they are both strict transporters of the purines adenine and guanine. In addition, SvNCS1 transports hypoxanthine, a unique function when compared to other known plant NCS1s.

Disciplines

Biology | Life Sciences

Heterologous Complementation in Yeast Reveals the Solute Specificity of the Nucleobase Cation Symporter 1 proteins of the plants Zea mays and Setaria viridis

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