Studies on a Widely Distributed Phage Tail-Derived Toxin Injection System

感染细菌的病毒（噬菌体或噬菌体）是地球上最丰富的生物实体。大多数的蜥蜴都有一个二十面体的头部，头部包含双链DNA基因组，头部的一个顶点上有一条“尾巴”。尾巴负责附着在宿主细菌上，并将基因组传递到细胞内部。因此，噬菌体尾部是非常复杂的纳米机器，能够特异性地结合细菌的外表面，穿透细胞壁和细胞膜，并将大分子（DNA和蛋白质）注入细胞质中。噬菌体尾作为大分子注射装置的巨大有效性已经导致它们被细菌出于各种目的而吸收，如VI型分泌系统所例示的，其是多种革兰氏阴性生物体中广泛存在的噬菌体尾衍生的毒力决定子。* 本提案的主题是另一种收缩性噬菌体尾衍生注射系统，称为光杆状病毒毒力盒（PVC）。尽管PVC在几乎所有细菌分支和古细菌中零星出现，但很少有人对其进行表征。除了与噬菌体尾蛋白类似的蛋白质外，PVC操纵子还编码通常与分泌系统相关的蛋白质，例如AAA ATP酶和毒素。两种不同的PVC已被证明可以杀死昆虫细胞，另一种可以刺激海洋管虫的形态发生。其他数百种不同PVC的功能尚不清楚。* 链霉菌属内的大多数细菌物种编码PVC，但从未对其进行过研究。我们已经发现PVC操纵子在一种链霉菌属物种内以细胞周期特异性方式表达，并且该操纵子编码噬菌体尾样实体。我们已经确定了不同的表型在PVC操纵子突变的菌株。我们未来的工作旨在揭示链霉菌中PVC的功能，确定单个PVC组分的生物化学性质和功能，并深入了解这些神秘结构在自然界中的一般作用。* 链霉菌生产各种各样的抗生素和其他有用的药物。我们的初步数据表明PVC在链霉菌抗生素生产中起作用，进一步了解这一功能可能对抗生素领域具有重要意义。此外，PVC代表了一种独特的可溶性蛋白质注射纳米机器，具有将蛋白质注射到各种真核细胞中的潜力。确定PVC如何靶向细胞将使我们能够将PVC引导到任何所需的细胞类型。类似地，破译PVC注射蛋白质的机制呈现出将任何所需蛋白质注射到靶细胞中的潜力。因此，通过我们的工作获得的知识将为工程PVC创造机会，用于各种新的生物技术目的，这些目的可能与农业，工业和人类健康有关。

The viruses that infect bacteria (bacteriophages or phages) are the most abundant biological entities on earth. Most phages possess an icosahedral head containing their double-stranded DNA genome and a “tail” attached to one vertex of the head. The tail is responsible for attaching to the host bacterium and delivering the genome to the interior of the cell. As such, phage tails are very complex nanomachines with the ability to specifically bind the outer surface of bacteria, penetrate the cell wall and membranes, and inject macromolecules (DNA and proteins) into the cytoplasm. The tremendous effectiveness of phage tails as macromolecular injection devices has led to their being co-opted by bacteria for a variety of purposes, as exemplified by the Type VI secretion system, which is a widespread phage tail-derived virulence determinant in diverse Gram-negative organisms. ***The subject of this proposal is another contractile phage tail-derived injection system known as the Photorhabdus Virulence Cassette (PVC). Few PVCs have been characterized despite their sporadic occurrence in almost all bacterial clades and in Archaea. In addition to proteins similar to phage tail proteins, PVC operons also encode proteins commonly associated with secretion systems, such as a AAA ATPases and toxins. Two different PVCs have been shown to kill insect cells and another stimulates morphogenesis of a marine tube worm. The functions of many hundreds of other diverse PVCs are unknown. ***Most bacterial species within the Streptomyces genus encode PVCs, but no studies have ever been undertaken on them. We have found that the PVC operon is expressed in a cell cycle specific manner within one Streptomyces species and that the operon encodes a phage tail-like entity. We have identified distinct phenotypes in strains bearing mutations in PVC operons. Our future work is aimed at uncovering the functions of PVCs in Streptomyces, determining the biochemical properties and functions of individual PVC components, and gaining insight into the general roles in nature of these mysterious structures. ***Streptomyces produce a huge diversity of antibiotics and other useful pharmaceuticals. Our preliminary data indicate that PVCs play a role in Streptomyces antibiotic production, and further insight into this function may be significant to the antibiotic field. Additionally, PVCs represent a unique, soluble protein injecting nanomachine with the potential to inject proteins into a variety of eukaryotic cells. Determining how PVCs target cells would allow us to direct PVCs to any desired cell type. Similarly, deciphering the mechanism by which PVCs inject proteins presents the potential to inject any desired protein into a targeted cell. Thus, the knowledge gained through our work will create opportunities to engineer PVCs for a variety of novel biotechnological purposes that could be relevant in agriculture, industry, and human health.