Poster abstracts

Poster number 25 submitted by Lana Bengez

Preferential Binding of Manganese Superoxide Dismutase to Single-stranded Nucleic Acids

Lana Bengez (John Carroll University Dept of Chemistry, Univ. Hts., OH 44118), Angela C. Smolik (John Carroll University Dept of Chemistry, Univ. Hts., OH 44118), David P. Mascotti (John Carroll University Dept of Chemistry, Univ. Hts., OH 44118)

Abstract:
Bacterial manganese superoxide dismutase (MnSOD) has been found to associate with double stranded DNA based on in situ immunostaining, gel retardation and nitrocellulose assays. Since then, no studies have been published with regard to MnSOD-RNA interactions. Also, no systematic variation of solution conditions, or thermodynamics, have been reported. We present evidence of fluorescence quenching upon binding single-stranded (ss) RNAs (poly(U), poly(C) and poly(A)) as well as double stranded plasmid DNA. We report the binding affinity (Kobs) as a function of monovalent salt concentration for each. Additionally, we have measured Kobs at different temperatures, leading to van’t Hoff enthalpy determinations, also as a function of [salt]. Surprisingly, at any given [salt], the binding affinity of MnSOD for ss RNAs is higher than for dsDNA, indicating that although MnSOD has the potential to bind chromosomal DNA, its main function may be to bind either single-stranded regions of DNA (e.g., at replication forks or transcription bubbles) or to mRNAs.

Keywords: Manganese Superoxide Dismutase, single-stranded RNA, fluorescence