- Suppression of linear side products by macromolecular crowding in nonribosomal enterobactin biosynthesis
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Nonribosomal enterobactin synthetase of Escherichia coli was found to prematurely release a large amount of linear precursors in an in vitro reconstitution. However, these side products are suppressed to negligible levels by polymeric cosolvents that create macromolecular crowding, a prominent feature of the intracellular environment. These findings show that macromolecular crowding is essential to normal functioning of the nonribosomal peptide synthetase and suggest that it may be crucial to btotechnological utilization of similar enzyme systems.
- Guo, Zu-Feng,Jiang, Ming,Zheng, Suilan,Guo, Zhihong
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- Structural change of the enterobactin synthetase in crowded solution and its relation to crowding-enhanced product specificity in nonribosomal enterobactin biosynthesis
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Significant conformational change is detected by circular dichroism and fluorimetry for the major component of the enterobactin synthetase in crowded solutions mimicking the intracellular environment. The structural change correlates well with the extent of the crowding-induced side product suppression in nonribosomal enterobactin synthesis. In contrast, protein-stabilizing solvophobic agents such as glycerol have no effect on the formation of side products, excluding crowding-induced protein stability as a cause for the observed enhancement of the product specificity of the synthetase. These results strongly support that macromolecular crowding is an indispensable physiological factor for normal functioning of the nonribosomal enterobactin synthetase by altering the active sites to increase its product specificity.
- Guo, Zu-Feng,Jiang, Ming,Zheng, Suilan,Guo, Zhihong
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p. 3855 - 3858
(2010/09/03)
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- Biosynthetic tailoring of microcin E492m: Post-translational modification affords an antibacterial siderophore-peptide conjugate
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The present work reveals that four proteins, MceCDIJ, encoded by the MccE492 gene cluster are responsible for the remarkable post-translational tailoring of microcin E492 (MccE492), an 84-residue protein toxin secreted by Klebsiella pneumonaie RYC492 that targets neighboring Gram-negative species. This modification results in attachment of a linearized and monoglycosylated derivative of enterobactin, a nonribosomal peptide and iron scavenger (siderophore), to the MccE492m C-terminus. MceC and MceD derivatize enterobactin by C-glycosylation at the C5 position of a N-(2,3-dihydroxybenzoyl)serine (DHB-Ser) moiety and regiospecific hydrolysis of an ester linkage in the trilactone scaffold, respectively. Mcel and MceJ form a protein complex that attaches C-glycosylated enterobactins to the C-terminal serine residue of both a C10 model peptide and full-length MccE492. In the enzymatic product, the C-terminal serine residue is covalently attached to the C4′ oxygen of the glucose moiety. Nonenzymatic and base-catalyzed migration of the peptide to the C6′ position affords the C6′ glycosyl ester linkage observed in the mature toxin, MccE492m, isolated from bacterial cultures.
- Nolan, Elizabeth M.,Fischbach, Michael A.,Koglin, Alexander,Walsh, Christopher T.
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p. 14336 - 14347
(2008/09/17)
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