National Institute of General Medical Sciences 2R35GM119707-11

Mapping the Structural Basis for Mechanistic Diversity in Metalloenzyme Superfamilies

This award funds research at Pennsylvania State University to study the structural basis for mechanistic diversity in metalloenzyme superfamilies. The project aims to understand how metalloproteins evolve and function with different metals, discover novel metal cofactors, and elucidate enzyme mechanisms relevant to biocatalysis and antibiotic development.

Description

Biomolecule interactions with transition metals are both extraordinarily selective and chemically powerful. Metalloproteins are critical as both important drug targets and useful reagents for various practical applications. To understand how metalloproteins evolve and adapt to use different metals (or none at all) when trace elements are scarce, or to elucidate how new enzyme activities arise in a given structural scaffold, members of large metalloprotein superfamilies that either share common cofactors or biological functions are studied. In a certain transition-metal driven essential biological transformation in DNA biosynthesis, divergent trace elements can be used for reaction initiation. Discovery of novel metal or radical cofactors used for these processes, and their mechanisms of assembly and deployment, will enable novel routes of enzyme inhibition in bacterial pathogens. In a second project, structures and reaction mechanisms in two different metalloenzyme superfamilies relevant to biocatalysis will be evaluated. These systems use common cofactors and reaction intermediates to catalyze divergent reaction outcomes, controlled by structural features of each enzyme. A deep understanding of the structural basis for mechanistic diversity will facilitate use of these enzymes in chemical synthesis applications. Finally, a third project focuses on understanding how metalloenzymes acquire their metallocofactors using periplasmic lanthanide trafficking proteins as a test case. These pathways represent a challenging molecular recognition problem, given the similarity in size and charge of ions in the lanthanide series. A deeper understanding of the structures of these metal-binding proteins could help understand how other biologically relevant metals are trafficked and sorted. Our comparative approach, driven by bioinformatics, structural studies, and collaborations with experts in protein functional and mechanistic characterization, provides detailed and testable hypotheses about the means by which distinct chemical reactions are accomplished. It has also resulted in discovery of entirely new families of metalloproteins and novel ways to control their activities and properties. Going forward, the goal is to advance this comparative approach to study metalloprotein function in more complex environments, such as within multiprotein complexes, allowing maximal leverage of fundamental structure-function insights in practical applications including evolution of biocatalysts, design of inhibitors as novel antibiotics, and development of protein reagents for rare-earth extraction.

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