SSRL and Stanford scientists, in collaboration with a team from UC Irvine, have gotten the first look into how the metal active center of an enzyme that is largely responsible for fertilizing plants is assembled. This enzyme, which is called nitrogenase, certain bacteria employ to turn nitrogen from the air into a form that plants can use for healthy growth. In contrast to the enzymatic reaction, manufacturing nitrogen fertilizer chemically requires extreme pressures and temperatures and thus huge amounts of energy.

The reduction of nitrogen takes place at the enzyme's core, a multicomponent complex called FeMoco made up of iron, molybdenum and sulfur. FeMoco is built by an "assembly line" of proteins outside of the enzyme. Researchers at the University of California, Irvine isolated a precursor to FeMoco bound to one of the assembly proteins toward the end of this "assembly line". Using x-ray absorption spectroscopy techniques at SSRL BL9-3, researchers revealed that at this stage in the assembly of FeMoco, the complex has not yet incorporated molybdenum atoms. This suggests that the iron core of FeMoco is assembled early on in the process, and that a simple reaction to add molybdenum is one of the last steps. This picture of one step in the pathway is the first time anyone has shown any of the steps in the assembly.

To learn more about this research see the full scientific highlight at:
http://www-ssrl.slac.stanford.edu/research/highlights_archive/FeMoco.html

M. C. Corbett, Y. Hu, A. W. Fay, M. W. Ribbe, B. Hedman and K. O. Hodgson, "Structural Insights into a Protein-bound Iron-Molybdenum Cofactor Precursor", Proc. Natl. Acad. Sci. USA 103, 1238 (2006)