Further Investigation Of The Biosynthesis And Function Of Rhodoquinone

Rhodoquinone (RQ) is an electron carrier that participates in the metabolic pathways of select species capable of anaerobic growth. Due to its importance in cellular metabolism, an understanding of the biosynthesis and regulation of RQ may precede novel anti-parasitic or anti-microbial drugs. An essential enzyme for RQ biosynthesis in some bacteria and protists is RquA, which converts the precursor ubiquinone (UQ) to RQ. To explore the alternative functions of RQ in metabolism and photosynthesis, Rhodospirillum rubrum served as a model organism for growth studies in liquid media. Wild-type R. rubrum was compared with a ΔrquA knockout. Semi-aerobic and anaerobic (dark and light) growth conditions were investigated using media enriched with the substrates succinate, fructose, pyruvate and acetate in the presence of bicarbonate or DMSO. These studies demonstrated that the ΔrquA strain was capable of dark anaerobic growth in the presence of select nutrients, but incapable of anaerobic growth in the light. To further characterize the RquA protein, RquA was tagged with a green fluorescent protein (GFP). When transformed with a plasmid containing the rquA gene, W303 yeast cells gain the ability to produce RQ.Yeast containing GFP-tagged RquA were imaged with fluorescent confocal microscopy with the goal of discerning the location of recombinant RquA in the yeast cells. These studies revealed alternative roles of RQ in bioenergetics and further elucidated the function of RquA.