5TGS image
Entry Detail
PDB ID:
5TGS
Keywords:
Title:
Crystal Structure of QueE from Bacillus subtilis with methionine bound
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2016-09-28
Release Date:
2017-01-18
Method Details:
Experimental Method:
Resolution:
2.55 Å
R-Value Free:
0.24
R-Value Work:
0.21
R-Value Observed:
0.21
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:7-carboxy-7-deazaguanine synthase
Chain IDs:A, B
Chain Length:263
Number of Molecules:2
Biological Source:Bacillus subtilis
Primary Citation
7-Carboxy-7-deazaguanine Synthase: A Radical S-Adenosyl-l-methionine Enzyme with Polar Tendencies.
J. Am. Chem. Soc. 139 1912 1920 (2017)
PMID: 28045519 DOI: 10.1021/jacs.6b11381

Abstact

Radical S-adenosyl-l-methionine (SAM) enzymes are widely distributed and catalyze diverse reactions. SAM binds to the unique iron atom of a site-differentiated [4Fe-4S] cluster and is reductively cleaved to generate a 5'-deoxyadenosyl radical, which initiates turnover. 7-Carboxy-7-deazaguanine (CDG) synthase (QueE) catalyzes a key step in the biosynthesis of 7-deazapurine containing natural products. 6-Carboxypterin (6-CP), an oxidized analogue of the natural substrate 6-carboxy-5,6,7,8-tetrahydropterin (CPH4), is shown to be an alternate substrate for CDG synthase. Under reducing conditions that would promote the reductive cleavage of SAM, 6-CP is turned over to 6-deoxyadenosylpterin (6-dAP), presumably by radical addition of the 5'-deoxyadenosine followed by oxidative decarboxylation to the product. By contrast, in the absence of the strong reductant, dithionite, the carboxylate of 6-CP is esterified to generate 6-carboxypterin-5'-deoxyadenosyl ester (6-CP-dAdo ester). Structural studies with 6-CP and SAM also reveal electron density consistent with the ester product being formed in crystallo. The differential reactivity of 6-CP under reducing and nonreducing conditions highlights the ability of radical SAM enzymes to carry out both polar and radical transformations in the same active site.

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