News & Events

Trixia M. Buscagan, Ph.D.

Posted on November 20, 2020


Date - November 20, 2020
1:00 pm - 2:00 pm


Postdoctoral Scholar in Chemistry
Division of Chemistry and Chemical Engineering
California Institute of Technology
Talk Title: Structural Evidence for Nitrogenase Metallocluster Modularity


Nitrogenase, the only enzyme capable of replenishing the nitrogen cycle, catalyzes dinitrogen reduction to ammonia. The most well-studied nitrogenase, Mo nitrogenase, consists of two component proteins, the Fe protein (a homodimer with a 4Fe4S cluster) and the MoFe protein (a heterotetramer with two complex metalloclusters per heterodimer). During catalysis, the two proteins associate, allowing ATP-dependent electron transfer from the Fe protein to the MoFe protein. The MoFe protein features a multimetallic active site (FeMoco), which binds and reduces N2 and other small molecule substrates. As shown by the X-ray crystal structure of the as-isolated MoFe protein, all the M centers of FeMoco are coordinatively saturated; thus, no obvious substrate binding site is available. To gain insight regarding potential labile ligands, that upon dissociation would generate a vacant site for substrate binding, our group has used Se-containing substrates. In my talk, I will present crystallographic evidence for Se-incorporation into nitrogenase clusters and discuss the mechanistic implications of these findings.