X-ray structure of an AdoMet radical activase reveals an anaerobic solution for formylglycine posttranslational modification
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Drennan_X-ray structure.pdf
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Author(s)
Goldman, Peter J.
McLaughlin, Martin I.
Drennan, Catherine L.
Grove, Tyler L.
Sites, Lauren A.
Booker, Squire J.
Date Issued
May 2013
Journal
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences (U.S.)
Citation
Goldman, P. J., T. L. Grove, L. A. Sites, M. I. McLaughlin, S. J. Booker, and C. L. Drennan. “X-ray structure of an AdoMet radical activase reveals an anaerobic solution for formylglycine posttranslational modification.” Proceedings of the National Academy of Sciences 110, no. 21 (May 21, 2013): 8519-8524.
Version
Final published version
Abstract
Arylsulfatases require a maturating enzyme to perform a co- or posttranslational modification to form a catalytically essential formylglycine (FGly) residue. In organisms that live aerobically, molecular oxygen is used enzymatically to oxidize cysteine to FGly. Under anaerobic conditions, S-adenosylmethionine (AdoMet) radical chemistry is used. Here we present the structures of an anaerobic sulfatase maturating enzyme (anSME), both with and without peptidyl-substrates, at 1.6–1.8 Å resolution. We find that anSMEs differ from their aerobic counterparts in using backbone-based hydrogen-bonding patterns to interact with their peptidyl-substrates, leading to decreased sequence specificity. These anSME structures from Clostridium perfringens are also the first of an AdoMet radical enzyme that performs dehydrogenase chemistry. Together with accompanying mutagenesis data, a mechanistic proposal is put forth for how AdoMet radical chemistry is coopted to perform a dehydrogenation reaction. In the oxidation of cysteine or serine to FGly by anSME, we identify D277 and an auxiliary [4Fe-4S] cluster as the likely acceptor of the final proton and electron, respectively. D277 and both auxiliary clusters are housed in a cysteine-rich C-terminal domain, termed SPASM domain, that contains homology to ~1,400 other unique AdoMet radical enzymes proposed to use [4Fe-4S] clusters to ligate peptidyl-substrates for subsequent modification. In contrast to this proposal, we find that neither auxiliary cluster in anSME bind substrate, and both are fully ligated by cysteine residues. Instead, our structural data suggest that the placement of these auxiliary clusters creates a conduit for electrons to travel from the buried substrate to the protein surface.
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.1302417110
