Structures of benzylsuccinate synthase elucidate roles of accessory subunits in glycyl radical enzyme activation and activity
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Funk-2014-Structures of benzyl.pdf
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Author(s)
Funk, Michael Andrew
Judd, Evan T.
Marsh, E. Neil G.
Elliott, Sean J.
Drennan, Catherine L
Date Issued
June 2014
Journal
Proceedings of the National Academy of Sciences of the United States of America
Publisher
National Academy of Sciences (U.S.)
Citation
Funk, Michael A., Evan T. Judd, E. Neil G. Marsh, Sean J. Elliott, and Catherine L. Drennan. “Structures of Benzylsuccinate Synthase Elucidate Roles of Accessory Subunits in Glycyl Radical Enzyme Activation and Activity.” Proceedings of the National Academy of Sciences 111, no. 28 (June 30, 2014): 10161–10166.
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Final published version
Abstract
Anaerobic degradation of the environmental pollutant toluene is initiated by the glycyl radical enzyme benzylsuccinate synthase (BSS), which catalyzes the radical addition of toluene to fumarate, forming benzylsuccinate. We have determined crystal structures of the catalytic α-subunit of BSS with its accessory subunits β and γ, which both bind a [4Fe-4S] cluster and are essential for BSS activity in vivo. We find that BSSα has the common glycyl radical enzyme fold, a 10-stranded β/α-barrel that surrounds the glycyl radical cofactor and active site. Both accessory subunits β and γ display folds related to high potential iron–sulfur proteins but differ substantially from each other in how they interact with the α-subunit. BSSγ binds distally to the active site, burying a hydrophobic region of BSSα, whereas BSSβ binds to a hydrophilic surface of BSSα that is proximal to the active site. To further investigate the function of BSSβ, we determined the structure of a BSSαγ complex. Remarkably, we find that the barrel partially opens, allowing the C-terminal region of BSSα that houses the glycyl radical to shift within the barrel toward an exit pathway. The structural changes that we observe in the BSSαγ complex center around the crucial glycyl radical domain, thus suggesting a role for BSSβ in modulating the conformational dynamics required for enzyme activity. Accompanying proteolysis experiments support these structural observations.
MIT Department
Massachusetts Institute of Technology. Department of Biology
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1073/pnas.1405983111
