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The natural product curacin A, a potent anticancer agent, contains a rare cyclopropane group. The five enzymes for cyclopropane biosynthesis are highly similar to enzymes that generate a vinyl chloride moiety in the jamaicamide natural product. The structural biology of this remarkable catalytic adaptability is probed with high-resolution crystal structures of the curacin cyclopropanase (CurF ER),...
This report presents the conclusions of the X-ray Validation Task Force of the worldwide Protein Data Bank (PDB). The PDB has expanded massively since current criteria for validation of deposited structures were adopted, allowing a much more sophisticated understanding of all the components of macromolecular crystals. The size of the PDB creates new opportunities to validate structures by comparison...
The virulence of Gram-positive bacteria is enhanced by toxins like the Streptococcus pyogenes β-NAD + glycohydrolase known as SPN. SPN-producing strains of S. pyogenes additionally express the protein immunity factor for SPN (IFS), which forms an inhibitory complex with SPN. We have determined crystal structures of the SPN-IFS complex and IFS alone, revealing that SPN is structurally related...
Modular polyketide synthases (PKS) make novel natural products through a series of preprogrammed chemical steps catalyzed by an assembly line of multidomain modules. Each assembly-line step involves unique extension and modification reactions, resulting in tremendous diversity of polyketide products. Dehydratase domains catalyze formation of an α,β-double bond in the nascent polyketide intermediate...
Background: Imidazole glycerol phosphate synthase catalyzes a two-step reaction of histidine biosynthesis at the bifurcation point with the purine de novo pathway. The enzyme is a new example of intermediate channeling by glutamine amidotransferases in which ammonia generated by hydrolysis of glutamine is channeled to a second active site where it acts as a nucleophile. In this case, ammonia reacts...
Background: The expression of pyrimidine nucleotide biosynthetic (pyr) genes in Bacillus subtilis is regulated by transcriptional attenuation. The PyrR attenuation protein binds to specific sites in pyr mRNA, allowing the formation of downstream terminator structures. UMP and 5-phosphoribosyl-1-pyrophosphate (PRPP), a nucleotide metabolite, are co-regulators with PyrR. The smallest RNA shown to bind...
Background: The cytochrome b 6 f complex functions in oxygenic photosynthesis as an integral membrane protein complex that mediates coupled electron transfer and proton translocation. The Rieske [2Fe-2S] protein subunit of the complex functions at the electropositive (p) membrane interface as the electron acceptor for plastoquinol and donor for the cytochrome f subunit, and may have a dynamic...
Background: Escherichia coli β-hydroxydecanoyl thiol ester dehydrase (dehydrase) is essential to the biosynthesis of unsaturated fatty acids, by shunting a 10-carbon intermediate from the saturated fatty acid pathway into the unsaturated fatty acid pathway. Dehydrase catalyzes reactions of dehydration and of double-bond isomerization on 10-carbon thiol esters of acyl carrier protein (ACP). The aim...
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