Interactions between the Azoarcus Ribozyme and Manganese (II) Divalent Cations

Abstract

The RNA world hypothesis suggests that RNA systems were the first form of life on the planet, beginning to appear approximately 4 billion years ago. Group I introns are self-splicing RNA elements in extant organisms and use Mg 2+ as the principle divalent cation to promote catalysis. The group I intron ribozyme from Azoarcus is frequently used in origin of life studies, partially due to its autocatalytic abilities-the Azoarcus ribozyme is able to be broken into fragments and reassemble itself into its fully functional ribozyme. Previous work [1] identified metal binding sites on the Azoarcus ribozyme which use both potassium and magnesium ions, and suggest that other divalent ions, such as manganese (II), may be capable of substituting for Mg 2+ in specific binding sites. The geological profile of the early earth suggests that manganese (II) was especially prevalent in nodules present on the ocean floor [2]. Compatibility with manganese (II) could have potentially offered a fitness advantage to early organisms occupying oceanic environments. We performed a series of experiments to demonstrate the catalytic ability of the Azoarcus ribozyme in various concentrations of MnCl 2 , using two different reaction mechanisms. We show that the catalytic activity of the Azoarcus ribozyme to be significantly improved when Mg 2+ was replaced with manganese (II), but only when reacted with exogenous oligonucleotide substrate.