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首页> 外文期刊>Biochemistry >Mutants of the Zinc Ligands of Lacticin 481 Synthetase Retain Dehydration Activity but Have Impaired Cyclization Activity
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Mutants of the Zinc Ligands of Lacticin 481 Synthetase Retain Dehydration Activity but Have Impaired Cyclization Activity

机译：乳酸锌配体的突变体481合成酶保留脱水活性但是环化活性受损

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摘要

Lantibiotics are ribosomally synthesized and post-translationally modified peptide antibiotics. The modifications involve dehydration of Ser and Thr residues to generate dehydroalanines and dehydrobutyrines, followed by intramolecular attack of cysteines onto the newly formed dehydro amino acids to produce cyclic thioethers. LctM performs both processes during the biosynthesis of lacticin 481. Mutation of the zinc ligands Cys781 and Cys836 to alanine did not affect the dehydration activity of LctM. However, these mutations compromised cyclization activity when investigated with full length or truncated peptide substrates. Mutation of His725, another residue that is fully conserved in lantibiotic cyclases, to Asn resulted in a protein that still catalyzed dehydration of the substrate peptide and also retained cyclization activity, but at a decreased level compared to that of the wild type enzyme. Collectively, these results show that the C-terminal domain of LctM is responsible for cyclization, that the zinc ligands are critical for cyclization, and that dehydration takes place independently from the cyclization activity. Furthermore, these mutant proteins are excellent dehydratases and provide useful tools to investigate the dehydration activity as well as generate dehydrated peptides for study of the cyclization reaction by wild type LctM.
机译：Lantibiotics是核糖体合成的和翻译后修饰的肽抗生素。修饰涉及Ser和Thr残基的脱水以产生脱氢胺和脱水丁胺，然后通过半胱氨酸的分子内发作到新形成的脱氢氨基酸上以产生环状硫醚。 LCTM在乳酸菌生物合成期间进行这两个过程。锌配体Cys781和Cys836至丙氨酸的突变不影响LCTM的脱水活性。然而，当用全长或截短的肽底物进行研究时，这些突变会受到环化活性。 HIS725的突变，另一个残余物，该残留物完全保守于毫突条子酶，导致ASN导致仍然催化基底肽的脱水并且还保留环化活性，但与野生型酶的水平降低。总的来说，这些结果表明，LCTM的C末端结构域负责环化，锌配体对环化至关重要，并且脱水独立于环化活性进行。此外，这些突变蛋白是优异的脱水酶，并提供有用的工具，以研究脱水活性以及产生脱水肽，用于通过野生型LCTM研究环化反应。

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