Phage Lysis

噬菌体对宿主细胞的裂解是生物圈中最常见的杀细胞事件， 基本过程。此外，了解噬菌体裂解的分子基础现在是临床相关的 因为噬菌体疗法正在成为对抗多重抗药性细菌感染的重要工具。 有两种通用模式：dsDNA测序仪使用的多基因裂解（MGL）和单基因裂解（SGL）， 所用的小单链核酸引物。至少，MGL系统需要壁溶酶， 内溶素，降解细胞壁或肽聚糖（PG），和一种小的膜蛋白，holin， 主动编程内溶素的功能。至少10种以上的噬菌体裂解蛋白也已被发现。 确定，包括在革兰氏阴性感染中破坏外膜的Spanins，或 作为洞蛋白和内溶素功能的调节剂。裂解途径具有响应和 引起宿主膜的生物物理变化，以及具有动态膜的多个实例 拓扑结构和大量的四级重排，最终导致细菌膜上的洞， 前所未有的微米级总的来说，这些复杂的MGL系统使裂解成为一种精确控制的、全或全过程的过程。 没有什么现象。 相比之下，小的ssDNA和ssRNA引物没有MGL系统的基因组空间。而是一个 Sgl（单基因裂解）蛋白的作用是引起宿主PG生物合成或稳态的功能障碍，最终导致宿主PG生物合成或稳态的功能障碍。 导致宿主自溶已经建立了一类阻断细胞壁生物合成步骤的Sgl， 被指定为蛋白质抗生素，但生物信息学鉴定的20多种其他Sgl的靶标， 噬菌体遗传学是未知的。 在接下来五年里，人们的注意力将不仅仅集中在那些在细胞分裂过程中融合细胞膜非凡的Spanins上 裂解，但也对两个新的类MGL蛋白：releasins和disruptin。版本在许可方面是独一无二的 内溶素的动态膜拓扑结构。干扰素是一种小两亲性蛋白质， 削弱外膜;令人惊讶的是，当纯化并在体外使用时，它们作为噬菌体编码的 由哺乳动物细胞产生的阳离子抗菌肽（CAMP）的变体。的独特功能 噬菌体遗传学将用于确定这两种新MGL蛋白的机制。我们的生物物理 和结构合作者将被提供突变体，表型和构建体，用于 在原子水平和感染的单细胞的背景下表征裂解。在西格里地区， 最近ssRNA微阵列宏基因组学的过度扩展将被用来解决许多 新的Sgl蛋白。假设ssRNA噬菌体Sgl蛋白已经进化到攻击宿主细胞的每一步 细胞壁合成和体内平衡。此外，一个新的模型，一个主要类别的Sgl的行为，结合通用细胞 将测试壁前体脂质II。

Lysis of the host cell by bacteriophage is, as the most frequent cytocidal event in the biosphere, a truly fundamental process. In addition, understanding the molecular basis of phage lysis is now clinically relevant because phage therapy is emerging as an important tool against multi-drug resistant bacterial infections. There are two general modes: Multi-Gene Lysis (MGL), used by dsDNA phages, and Single-Gene Lysis (SGL), used by small single-strand nucleic acid phages. At minimum, MGL systems require a muralytic enzyme, the endolysin, that degrades the cell wall or peptidoglycan (PG), and a small membrane protein, the holin, that actively programs the function of the endolysin. At least 10 more classes of phage lysis proteins have also been identified, including spanins functioning in destruction of the outer membrane in Gram-negative infections or acting as regulators of holin and endolysin function. The lysis pathways have steps that both respond to and cause biophysical changes in the host membrane, as well as featuring multiple examples of dynamic membrane topology and massive quaternary rearrangements, ultimately resulting in holes in the bacterial membrane of unprecedented micron-scale. Overall, these complex MGL systems make lysis a precisely-controlled, all-or- nothing phenomenon. In contrast, the small ssDNA and ssRNA phages have no genomic room for MGL systems. Instead a single Sgl (single gene lysis) protein acts to cause dysfunction in host PG biosynthesis or homeostasis, eventually leading to a host autolysis. One class of Sgl’s that block steps in cell wall biosynthesis has been established and designated as Protein Antibiotics, but the target of more than 20 other Sgl’s identified by bioinformatics and phage genetics is not known. In the next five years, the focus will not only be on the remarkable spanins, which fuse membranes during lysis, but also on two new classes of MGL proteins: releasins and disruptins. Releasins are unique in licensing dynamic membrane topology of endolysins. Disruptins are small, amphipathic proteins that are used to weaken the outer membrane; surprisingly, when purified and used in vitro, they function as phage-encoded versions of the cationic antimicrobial peptides (CAMPs) produced by mammalian cells. The unique power of phage genetics will be used to determine the mechanisms of both these new MGL proteins. Our biophysical and structural collaborators will be supp;oed with mutants, phenotypes and constructs to be used in characterizing lysis at both the atomic level and in the context of the infected single cell. In the SGL area, the recent hyper-expansion of the metagenomics of ssRNA phages will be exploited to solve the targets of many new Sgl proteins. The hypothesis is that ssRNA phage Sgl proteins have evolved to attack every step in host cell wall synthesis and homeostasis. Also, a new model that a major class of Sgl’s acts by binding the universal cell wall precursor, Lipid II, will be tested.