With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Robert Hausinger and Dr. Jian Hu from Michigan State University to characterize how a microorganism interconverts the two mirror image structures of lactic acid, a central element of carbohydrate metabolism. The enzyme that does this, called lactate racemase, requires both a protein component and nickel. Nickel is very rarely found in biology. Even more remarkably, the nickel in lactate racemase is present in a unique environment never before observed. This project investigates how the bacterium makes the cofactor that creates the unique environment. This effort provides training to a postdoctoral researcher, a graduate student, and undergraduate students in the areas of structure and biochemical mechanisms. These researchers also participate in hands-on educational activities for the public related to this topic that will engage lifelong learners of all ages at the annual Science Festival at the university.

This research elucidates structure-function aspects of the four proteins required for lactate racemase activity. It characterizes how LarB catalyzes a new reaction, carboxylation of the pyridinium ring of nicotinic acid adenine dinucleotide while hydrolyzing the phosphoanhydride linkage to produce pyridinium-3,5-dicarboxylic acid mononucleotide. Additional studies of LarE, a sacrificial sulfur transferase, establish how the two carboxylic acid groups are transformed into thiocarboxylate groups and define whether the resulting dehydroalanine side chain of the enzyme can be regenerated to cysteine. This work uncovers how LarC catalyzes the CTP-dependent installation of Ni into pyridinium-3-5-dithiocarboxylic acid mononucleotide, the first biological example of a cyclometallation reaction, to create the cofactor. Finally, these investigations show how the cofactor is bound to different LarA species and identifies other potential transformations catalyzed by the enzyme. In combination, the biosynthesis and roles of this novel nickel-containing cofactor can be described. This innovative research expands our understanding of nickel biochemistry and establishes a new paradigm for redox chemistry involving a tethered nickel-pincer cofactor.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Agency
National Science Foundation (NSF)
Institute
Division of Chemistry (CHE)
Type
Standard Grant (Standard)
Application #
1807073
Program Officer
Pui Ho
Project Start
Project End
Budget Start
2018-07-01
Budget End
2021-06-30
Support Year
Fiscal Year
2018
Total Cost
$567,000
Indirect Cost
Name
Michigan State University
Department
Type
DUNS #
City
East Lansing
State
MI
Country
United States
Zip Code
48824