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- Title
Radical SAM enzyme QueE defines a new minimal core fold and metal-dependent mechanism.
- Authors
Dowling, Daniel P; Bruender, Nathan A; Young, Anthony P; McCarty, Reid M; Bandarian, Vahe; Drennan, Catherine L
- Abstract
7-carboxy-7-deazaguanine synthase (QueE) catalyzes a key S-adenosyl-L-methionine (AdoMet)- and Mg2+-dependent radical-mediated ring contraction step, which is common to the biosynthetic pathways of all deazapurine-containing compounds. QueE is a member of the AdoMet radical superfamily, which employs the 5′-deoxyadenosyl radical from reductive cleavage of AdoMet to initiate chemistry. To provide a mechanistic rationale for this elaborate transformation, we present the crystal structure of a QueE along with structures of pre- and post-turnover states. We find that substrate binds perpendicular to the [4Fe-4S]-bound AdoMet, exposing its C6 hydrogen atom for abstraction and generating the binding site for Mg2+, which coordinates directly to the substrate. The Burkholderia multivorans structure reported here varies from all other previously characterized members of the AdoMet radical superfamily in that it contains a hypermodified (β6/α3) protein core and an expanded cluster-binding motif, CX14CX2C.
- Subjects
GUANINE; SYNTHASES; RADICALS (Chemistry); METHIONINE; ADENOSYLMETHIONINE; MAGNESIUM ions; CRYSTAL structure
- Publication
Nature Chemical Biology, 2014, Vol 10, Issue 2, p106
- ISSN
1552-4450
- Publication type
Article
- DOI
10.1038/nchembio.1426