Investigation into the antibiotic activity of the lantibiotic haloduracin

描述（由申请人提供）：抗生素是核糖体产生的，翻译后修饰的具有抗生素活性的肽天然产物。许多表现出独特的作用模式，通过靶向细菌肽聚糖合成的高度保守步骤和/或破坏细胞壁和质膜。鉴于这些结构对细胞活力的重要性，值得注意的是，抗生素似乎避开了典型的耐药途径。因此，它们对耐甲氧西林金黄色葡萄球菌（MRSA）和耐万古霉素肠球菌（VRE）等病原体仍然有效。由于抗菌素耐药性对人类健康的威胁越来越大，抗生素作为治疗感染的潜在药物受到越来越多的关注。lan抗生素的特点是存在衣硫氨酸（Lan）和甲基衣硫氨酸（MeLan）环。这些不寻常的结构特征源于翻译后前体肽的酶修饰。前体肽中存在的丝氨酸和苏氨酸残基的酶脱水分别产生脱氢丙氨酸和脱氢丁氨酸部分。半胱氨酸残基对脱水残基的michael型加成产生独特的Lan和MeLan环。在一些系统中，一个单一的双功能酶（LanM）既负责脱水又负责环化。基因编码生物合成途径的简便性为重组抗生素机制以产生具有更好治疗潜力的化合物提供了一个非凡的机会。由于基因组信息的不断增加，已经有了

DESCRIPTION (provided by applicant): Lantibiotics are ribosomally produced, post translationally modified peptide natural products with antibiotic activity. Many exhibit unique modes of action by targeting highly conserved steps in bacterial peptidoglycan synthesis and/or disrupting the cell wall and plasma membrane. Given the importance of these structures to cellular viability, it is noteworthy that lantibiotics appear to elude the typical resistance pathwys. Thus, they remain potent against pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Due to the increasing threat of antibacterial resistance to human health, lantibiotics have been receiving increased consideration as potential treatments for infection. Lantibiotics are characterized by the presence of lanthionine (Lan) and methyllanthionine (MeLan) rings. These unusual structural features arise from the posttranslational, enzymatic modification of precursor peptides. Enzymatic dehydration of serine and threonine residues present in the precursor peptide yield dehydroalanine and dehydrobutyrine moieties, respectively. Michael-type addition of cysteine residues to the dehydrated residues produces the distinctive Lan and MeLan rings. In some systems a single bifunctional enzyme (LanM) is responsible for both dehydration and cyclization. The brevity of the genetically encoded biosynthetic pathways provides a remarkable opportunity for reengineering the lantibiotic machinery to generate compounds with improved therapeutic potential. Facilitated by the increasing availability of genomic information, there has been an explosion of newly discovered lantibiotic gene clusters. One of the more intriguing findings is a class of two-component lantibiotics that segregate cellular targeting from antimicrobial activity. For example, the two units of haloduracin (Hal¿ and Hal¿) act in synergy to achieve nanomolar activity against a range of Gram-positive organisms. Hal¿ is proposed to bind the peptidoglycan precursor lipid II, leading to the recruitment of Hal¿, pore formation and membrane disruption. However, molecular details about the interactions that lead to the potent bioactivity of haloduracin are lacking. Thus, the long-term goal of this proposal is to establish te mode of action of two-component lantibiotics and to use that knowledge to generate improved lantibiotics. To this end, the LanM enzymes that produce haloduracin will be engineered to generate constitutively active lantibiotic synthetases capable of producing analogues from chemically synthesized linear peptides. This methodology will allow the incorporation of non-natural features that will expand the chemical space beyond that accessible to Nature. Wild-type haloduracin and new analogues will be evaluated to uncover chemical features that enhance (or degrade) binding between haloduracin and its targets. The results of this work will enhance the mechanistic understanding of lantibiotic bioactivity, which may guide the development of new antibacterial compounds.