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At the confluence of ribosomally synthesized peptide modification and radical S-adenosylmethionine (SAM) enzymology.

ABSTRACT: Radical S-adenosylmethionine (RS) enzymology has emerged as a major biochemical strategy for the homolytic cleavage of unactivated C-H bonds. At the same time, the post-translational modification of ribosomally synthesized peptides is a rapidly expanding area of investigation. We discuss the functional cross-section of these two disciplines, highlighting the recently uncovered importance of protein-protein interactions, especially between the peptide substrate and its chaperone, which functions either as a stand-alone protein or as an N-terminal fusion to the respective RS enzyme. The need for further work on this class of enzymes is emphasized, given the poorly understood roles performed by multiple, auxiliary iron-sulfur clusters and the paucity of protein X-ray structural data.

SUBMITTER: Latham JA

PROVIDER: S-EPMC5633103 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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At the confluence of ribosomally synthesized peptide modification and radical <i>S</i>-adenosylmethionine (SAM) enzymology.

Latham John A JA Barr Ian I Klinman Judith P JP

The Journal of biological chemistry 20170822 40

Radical <i>S</i>-adenosylmethionine (RS) enzymology has emerged as a major biochemical strategy for the homolytic cleavage of unactivated C-H bonds. At the same time, the post-translational modification of ribosomally synthesized peptides is a rapidly expanding area of investigation. We discuss the functional cross-section of these two disciplines, highlighting the recently uncovered importance of protein-protein interactions, especially between the peptide substrate and its chaperone, which fun ...[more]

PMID: 28830931

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Project description:A [4Fe-4S](+) cluster reduces a bound S-adenosylmethionine (SAM) molecule, cleaving it into methionine and a 5'-deoxyadenosyl radical (5'-dA(•)). This step initiates the varied chemistry catalyzed by each of the so-called radical SAM enzymes. The strongly oxidizing 5'-dA(•) is quenched by abstracting a H-atom from a target species. In some cases, this species is an exogenous molecule of substrate, for example, L-tyrosine in the [FeFe] hydrogenase maturase, HydG. In other cases, the target is a proteinaceous residue as in all the glycyl radical forming enzymes. The generation of this initial radical species and the subsequent chemistry involving downstream radical intermediates is meticulously controlled by the enzyme so as to prevent unwanted reactions. But the manner in which this control is exerted is unknown. Electron paramagnetic resonance (EPR) spectroscopy has proven to be a valuable tool used to gain insight into these mechanisms. In this Account, we summarize efforts to trap such radical intermediates in radical SAM enzymes and highlight four examples in which EPR spectroscopic results have shed significant light on the corresponding mechanism. For lysine 2,3-aminomutase, nearly each possible intermediate, from an analogue of the initial 5'-dA(•) to the product radical L-β-lysine, has been explored. A paramagnetic intermediate observed in biotin synthase is shown to involve an auxiliary [FeS] cluster whose bridging sulfide is a co-substrate for the final step in the biosynthesis of vitamin B7. In HydG, the L-tyrosine substrate is converted in unprecedented fashion to a 4-oxidobenzyl radical on the way to generating CO and CN(-) ligands for the [FeFe] cluster of hydrogenase. And finally, EPR has confirmed a mechanistic proposal for the antibiotic resistance protein Cfr, which methylates the unactivated sp(2)-hybridized C8-carbon of an adenosine base of 23S ribosomal RNA. These four systems provide just a brief survey of the ever-growing set of radical SAM enzymes. The diverse chemistries catalyzed by these enzymes make them an intriguing target for continuing study, and EPR spectroscopy, in particular, seems ideally placed to contribute to our understanding.

Dataset Information

At the confluence of ribosomally synthesized peptide modification and radical S-adenosylmethionine (SAM) enzymology.

Publications

At the confluence of ribosomally synthesized peptide modification and radical <i>S</i>-adenosylmethionine (SAM) enzymology.

Similar Datasets

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