The importance of the leader sequence for directing lanthionine formation in lacticin 481
The importance of the leader sequence for directing lanthionine formation in lacticin 481
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DOI：
10.1021/bi800277d
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发表时间：
2008-07-15
期刊：
影响因子：
2.9
通讯作者：
van der Donk, Wilfred A.
中科院分区：
文献类型：
--
作者：
Patton, Gregory C.;Paul, Moushumi;van der Donk, Wilfred A.
抗生素是由N-末端前导序列和C-末端前肽合成的翻译后修饰的多肽抗菌剂。它们的成熟过程包括前体多肽中的丝氨酸和苏氨酸残基的酶促脱水生成不饱和氨基酸，不饱和氨基酸与附近的半胱氨酸在分子内反应生成环状硫醚，称为羊硫醚和甲基羊硫醚。前导肽在抗生素生物合成中的作用一直受到很多人的猜测。在本研究中，LctA前体多肽(LctA)前导序列的保守残基突变并没有抑制LctM的脱水和环化反应，这表明没有一个特定残基是这些转化所必需的。因此，这些氨基酸可能在第二类抗生素的前导序列中保守，以指导其他生物合成事件，如前导肽的蛋白分解或活性化合物的细胞外运输。然而，在前导肽中引入Pro残基强烈影响了脱水效率，这与合成酶对前导肽二级结构的识别是一致的。此外，Leu-7位置上疏水残基的存在对于酶处理来说似乎是重要的。基于本工作中的数据和前人的研究，提出了LCTM和LCTA相互作用的模型。目前的研究还展示了使用乳糖素481合成酶制备H类乳糖素481家族的其他抗生素的能力，包括努卡星ISK-1、变形菌素II和反胃球菌素A。令人惊讶的是，位于许多II类抗生素中似乎保守的环上的Glu，包括那些不属于lacticin 481亚组的抗生素，对lacticin 481的抗菌活性并不是必需的。
Lantibiotics are post-translationally modified peptide antimicrobial agents that are synthesized with an N-terminal leader sequence and a C-terminal propeptide. Their maturation involves enzymatic dehydration of Ser and Thr residues in the precursor peptide to generate unsaturated amino acids, which react intramolecularly with nearby cysteines to form cyclic thioethers termed lanthionines and methyllanthionines. The role of the leader peptide in lantibiotic biosynthesis has been subject to much speculation. In this study, mutations of conserved residues in the leader sequence of the precursor peptide for lacticin 481 (LctA) did not inhibit dehydration and cyclization by lacticin 481 synthetase (LctM) showing that not one specific residue is essential for these transformations. These amino acids may therefore be conserved in the leader sequence of class II lantibiotics to direct other biosynthetic events, such as proteolysis of the leader peptide or transport of the active compound outside the cell. However, introduction of Pro residues into the leader peptide strongly affected the efficiency of dehydration, consistent with recognition of the secondary structure of the leader peptide by the synthetase. Furthermore, the presence of a hydrophobic residue at the position of Leu-7 appears important for enzymatic processing. Based on the data in this work and previous studies, a model for the interaction of LctM with LctA is proposed. The current study also showcases the ability to prepare other lantibiotics in the class H lacticin 481 family, including nukacin ISK-1, mutacin II, and ruminococcin A using the lacticin 481 synthetase. Surprisingly, a conserved Glu located in a ring that appears conserved in many class II lantibiotics, including those not belonging to the lacticin 481 subgroup, is not essential for antimicrobial activity of lacticin 481.