Investigation of Molybdenum Cofactor through Chemical, Biochemical and Biophysical Studies

The molybdenum cofactor (Moco) is an essential biomolecule for all forms of life. Numerous
enzymes rely on the proper functioning of Moco for normal physiological functions. Failures to
biosynthesize Moco cause severe physiological distress and even childhood death. Outside the
protein environment, this cofactor is unstable and has not yet been chemically synthesized. The
Moco has several redox active components, and together, these components can carry out up to
ten-electron chemistry, while in most cases, the substrate transformation requires only two
electrons. To understand how different components stabilize the electronic structure that supports
reactivity, we will investigate discrete molecules with defined features. The work outlined in this
proposal seeks to complete the synthesis of the closest chemical mimic of Moco. While in the
reduced state, Moco is unstable outside the protein environment, and how it is stabilized within a
protein is not clear. The proposal also seeks to understand the geometric and electronic
properties of Moco in the DMSO reductase family of enzymes using periplasmic nitrate reductase
(NapA) and its variants as a model through biochemical and biophysical studies. The specific
aims of the proposal are: 1) to synthesize pterin Mo-centers and Mo=X (X=S, O) complexes
allowing investigation of their geometric and electronic structures in relation to reactivity; 2) to
understand the geometric, electronic, and functional properties of the Mo-center in the DMSOR
family using NapA as a model. Overall, new important molecular-level knowledge will be
generated about the structure-function of a class of enzymes important to human health.

Grant Number: 2R15GM139064-02
NIH Institute/Center: NIH
Principal Investigator: PARTHA BASU