18. PK and NRP Synthases 4 | Summary and Q&A

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August 1, 2019
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18. PK and NRP Synthases 4

TL;DR

A comprehensive analysis of the biosynthesis of enterobactin, a siderophore produced by E. coli, explores the roles of different proteins and domains in the assembly line, including adenylation domains and thioesterase domain.

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Questions & Answers

Q: What is enterobactin and why is it important?

Enterobactin is a siderophore produced by E. coli and other bacteria to scavenge iron, an essential but scarce nutrient. It acts as a metal chelator to acquire iron from the environment.

Q: How is enterobactin biosynthesized?

Enterobactin is synthesized through an assembly line mechanism involving different proteins and domains. Adenylation domains (EntE and EntF) activate and transfer monomers, a carrier protein (EntB) transports monomers, and a thioesterase domain catalyzes ester linkages to form the final product.

Q: What role does the Ppant arm play in enterobactin biosynthesis?

The Ppant arm is a post-translational modification that is added to carrier proteins (T domains) by the PPTase enzyme EntD. It allows the carrier protein to transport monomers and facilitates the biosynthesis of enterobactin.

Q: How was the biosynthesis of enterobactin studied experimentally?

Various experiments, including ATP-PPi exchange assays, radiolabeling studies, and HPLC analysis, were conducted to characterize the functions of different proteins and domains involved in the biosynthesis of enterobactin.

Q: Why is enterobactin considered an iterative assembly line?

Enterobactin biosynthesis involves the same carrier protein (EntF) and catalytic domain (C domain) being used multiple times to elongate the chain. This is a characteristic of an iterative assembly line, as opposed to non-iterative assembly lines where each step has its own module.

Summary & Key Takeaways

  • Enterobactin is a siderophore produced by E. coli and other gram-negative bacteria that serves as a metal chelator to acquire iron, which is essential but scarce in the environment.

  • The biosynthesis of enterobactin involves the action of different proteins and domains, including adenylation domains (EntE and EntF) that activate and transfer monomers, a thioesterase domain that catalyzes ester linkages, and a carrier protein (EntB) that transports monomers.

  • Experiments have been conducted to characterize the functions of these proteins and domains, including ATP-PPi exchange assays, radiolabeling studies, and HPLC analysis.

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