DEFENSINS, BACTENECINS AND PERIODONTAL DISEASES

这个项目的长期目标是系统地研究 “防御素和杆菌素”的结构和分子生物学 丹参颗粒中存在的抗菌阳离子多肽 中性粒细胞。这些研究将有助于确定、设计、开发和 评估一类新的无毒抗生素用于预防 牙周病原体包括伴生放线杆菌和 牙龈卟啉单胞菌以及条件致病菌 白色念珠菌。 防御素和杆菌素被输送到含有 吞噬过程中摄取的微生物，并被释放到 中性粒细胞被促分泌剂刺激时的细胞外液。 它们与微生物的膜相互作用，改变膜的通透性 和离子梯度，并进一步导致功能的损害 呼吸链和其他内部的能量依赖活动 膜。它们在宿主防御、炎症和 通过它们的杀戮能力恢复改变的动态平衡状态 入侵的微生物。这表明了选择这些项目的理由 我们目前研究的分子以及这些分子的重要性 控制包括牙周在内的这些微生物的口腔感染 疾病。 高度保守的二硫化物、甘氨酸和带电残基 防御素和重复的Pro-Arg-Pro三联体 杆菌素中的疏水残基为这些提供了刚性结构 克服微生物对有机物质的适应性耐药性的分子 抗生素。这些独特的保守结构元素也表明 它们的杀菌功能确实依赖于一种特定的 结构特征和特殊的电荷分布。结构性的 在这些多肽的初级序列中观察到的多样性是 反映在它们生物活性的巨大差异上。这 功能多样性显然是由于 它们的大小、序列、精细结构基序和侧链形貌 分子。该项目涉及合成防御素、杆菌毒素和 通过化学和基因工程技术获得的多肽类似物， 用波谱方法(核磁共振、傅里叶变换红外光谱、圆二色谱)测定结构 计算机模拟和晶体结构分析，以及In的评估 这些分子的体外杀灭活性。 从结构-功能分析中获得的信息将 允许设计和合成立体化学限制的多肽 防御素和杆菌素的类似物，可诱导增强和 长时间的活动。这些新的口服抗生素可能对 控制和治疗牙周病和其他口腔感染。 此外，分子生物学研究将描绘出cdna和 编码活性类似物和铅序列的重组DNA 到类似临床应用的基因治疗方法。

The long range goal of this project is to systematically study the structural and molecular biology of "defensins and bactenecins", the antimicrobial cationic polypeptides present in the granules of neutrophils. These studies will help identify, design, develop and evaluate a new class of nontoxic antibiotics to be used to defend against periodontal pathogens including Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis as well as opportunistic pathogens such as Candida albicans. Defensins and bactenecins are delivered to vacuoles containing the ingested microorganisms during phagocytosis and are released into the extracellular fluids when neutrophils are stimulated by secretagogues. They interact with the membranes of microbes, alter membrane permeability and ionic gradient, and further cause impairment of the function of the respiratory chain and other energy dependent activities in the inner membranes. They play a major role in host defense, inflammation and restoration of the altered homeostatic condition by their ability to kill invading microbes. This suggests a rationale for selection of these molecules for our present studies and the importance of these molecules in controlling oral infections by these organisms including periodontal disease. The highly conserved disulfides, glycines and the charged residues in defensins, and the repeating Pro-Arg-Pro triplets spaced by a single hydrophobic residue in bactenecins, provide rigid structures for these molecules to overcome the adaptive microbial resistance to organic antibiotics. These unique conserved structural elements also suggest that their microbicidal functions are indeed dependent on a specific structural feature and a particular charge distribution. The structural diversity observed in the primary sequence of these polypeptides is reflected in wide variations in their biological activity. This functional diversity is clearly a consequence of subtle variations in the size, sequence, fine structural motifs and side-chain topography of these molecules. This project involves synthesis of defensins, bactenecins and peptide analogs by both chemical and genetic engineering techniques, structure determination by spectroscopic methods (NMR, FTIR, CD), computer modeling and crystal structure analysis, and assessment of in vitro cidal activity of these molecules. The information to be obtained from structure-function analyses will permit the design and synthesis of stereochemically constrained peptide analogs of defensins and bactenecins which could elicit enhanced and prolonged activity. These new oral antibiotics may be useful for the control and treatment of periodontal disease and other oral infections. In addition, the molecular biology studies would delineate the cDNA and the recombinant DNA encoding the sequences of the active analogs and lead to gene therapy approaches for similar clinical applications.