In vitro Activity of Supercoiled Double Stranded DNA Cleavage by Proteins Extracted from Sweet Potato (Ipomea Batatas L.) Peel

Abstract

This research was aimed to identify the presence of RIPs (Ribosome InactivatingProteins) in sweet potato (Ipomea batatas L.) through its activity test to cleave thesupercoiled double stranded DNA. The leaf, tuber and peel of white, yellow, and purplesweet potatoes were extracted using 5 mM sodium phospate buffer (pH 7) containing 0.14M sodium chloride then were precipitated using amonium sulfate and were purified bydialysis. Each extract was measured its protein contents with Lowry method using BSAsolution as standard. The activity of supercoiled DNA cleaved was determined using pUC 19plasmid DNA. The activity test was done using agarose gel electrophoresis by observing 3criterions viz. the decreasing thinkness band of supercoiled DNA, the band of circular formthickening and the appearance of the linear band which were subsequently compared to theplasmid DNA without treatment. The extract of Mirabilis jalapa leaf was used as a positivecontrol. The result showed that only peel of white, yellow, and purple sweet potato had RIPsactivity in cleaving the supercoil DNA. Increasing concentrations of the crude extractresulted in increasing the activity, which was indicated by the decreasing thinkness band ofsupercoiled DNA, and the thickening of circular and linear band.

Key words: Ribosome-Inactivating Proteins (RIPs), sweet potato (Ipomea batatas L.), andsupercoil DNA