Putative Arginine Kinase

Abstract

A recent genome blast conducted by Fraga et al. has revealed the possibility of an arginine kinase in several proteobacteria. This study was undertaken to characterize the putative arginine kinase discovered in Myxococcus Xanthus. Arginine kinases serve to catalyze the transfer of a high‐energy phosphoryl group from ATP to the specific guanidino compound arginine. Arginine kinase belongs to a family of proteins known as phosphagen kianses, which are widely distributed and conserved enzymes amongst metazoan and some protozoan organisms, but are rarely found in bacteria. Ross Ellington has extensively reviewed the role of this enzyme and suggests phosphagen kinases play a vital role in energy homeostasis. Myxococcus Xanthus has a complex development cycle forming fruiting bodies upon starvation that give rise to spores. The development cycle is mediated through a complex signaling pathway that may potentially require a significant amount of energy to initiate. To test this hypothesis the putative arginine kinase gene was knocked out of Myxococcus Xanthus by homologous recombination and subjected to a series of phenotypic assays measuring its responses to ionic and osmotic stress. In the development assays without ionic or osmotic stress the knock out (KO) strain was unable to develop, or formed aberrant fruiting bodies. Interestingly, the KO strain was rescued when the development assay contained either .3M KCl or .3M sucrose. Another phenotypic assay subjected the WT and the KO strain to ionic and osmotic stress during the vegetative stage. Doubling times were measured and the KO strain had a considerably higher generation time than the WT. This suggests the possibility that the putative arginine kinase is involved in energy regulation or may be involved in a development pathway.