Scientists in Montana have uncovered evidence that the ancestral nitrogen-fixing enzyme, nitrogenase, evolved employing molybdenum, rather than vanadium or iron.
N2 has been the principle component of air for more than two billion years, but this nitrogen is biologically inaccessible until it is “fixed” by transforming it into nitric oxide (NO) or ammonia (NH3), a process which only occurs with the energy of a lightning strike or, in some instances, a mineral-catalyzed reaction with ferrous sulfide. Fundamental building blocks such as DNA and amino acids require nitrogen, and the evolution of nitrogen-fixing enzymes provided a solution to a severely limiting nutrient. Sifting through the genetic code and the molecular structures of modern nitrogenases, Dr. Peters’ group traced the evolutionary paths to the earliest probable common ancestor: hydrogen-consuming, methane-producing archaea.
Understanding these first steps made by early life to harvest crucial, yet previously scarce elements from the surroundings adds new details to the story of how life evolved on Earth, and how it might evolve elsewhere. ~K.E.D.C.