A team of researchers at the Goethe University in Frankfurt has successfully purified the Rnf complex from the anaerobic fermentic thermophilic bacterium Thermotoga maritima. Their results—published today in Nature—provide biochemical proof and bioenergetic characterization of the primitive Rnf enzyme and help explain how primitive organisms might have developed ATP.
"We already saw ten years ago that there are genes in these microbes that perhaps encode for a primordial respiration enzyme,” says co-author Volker Müller. "Since then, we—as well as other groups worldwide—have attempted to prove the existence of this respiratory enzyme and to isolate it. For a long time unsuccessfully because the complex was too fragile and fell apart at each attempt to isolate it from the membrane. We found the fragments, but were unable to piece them together again."After succesfully purifying and isolating Rnf, they were able to demonstrate how the enzyme complex functions much like a pumped-storage plant that produces electricity via turbines—the enzyme transports sodium ions out of the cells interior through the membrane to the outside and in the process an electric field is produced. The electric field is then used to drive ATP synthase, by allowing the sodium ions to flow back along the field into the cell’s interior and obtaining ATP in doing so.
"Our studies thus radiate far beyond the organism Thermotoga maritima under investigation and are extremely important for bacterial physiology in general," explains Müller, highlighting the importance to use this knowledge to better understand exactly how the Rnf enzyme works and what role the individual parts play. "I'm happy to say that we're well on the way here, since we're meanwhile able to produce the Rnf enzyme ourselves using genetic engineering methods," he concludes.