Structure and size determination of S. aureus pathogenicity island capsids

描述（由申请人提供）：金黄色葡萄球菌产生许多具有重要医学意义的毒素，包括中毒性休克综合征毒素（TSST-1）和肠毒素B和c。其中一些毒素携带在所谓的致病性岛屿上，这些毒素是类似于噬菌体的遗传元件，但不携带通常与噬菌体活性相关的大多数基因。这些元素通常是高度稳定的，但特定的噬菌体有能力切除它们并将它们包装成噬菌体颗粒，从而将毒素基因转移到新细胞中。SaPI1是金黄色葡萄球菌的致病性岛，携带TSST-1基因以及肠毒素Q和L. SaPI1被噬菌体80？，并有效地包装成噬菌体样颗粒，使用80？结构蛋白。然而，SaPI1衣壳只有正常80？衣壳，与其较小的基因组相称。目前尚不清楚大小决定的机制是什么，但该系统类似于大肠杆菌噬菌体P2/P4系统，其中卫星噬菌体P4劫持P2的结构蛋白并利用它们包装更小的衣壳。本研究的总体目的是了解金黄色葡萄球菌噬菌体80？/Sal1系统及其在细菌发病机制发展中的作用在这项研究中，我们将使用低温电子显微镜和三维重建方法来确定噬菌体80？和SaPI1粒子。本研究的具体目的是：(1)确定金黄色葡萄球菌噬菌体80的三维结构。衣壳;(2)确定SaPI1衣壳的三维结构；(3)确定共表达80？/SaPI1结构蛋白。与公共卫生相关：金黄色葡萄球菌已成为医院的主要健康问题，特别是随着多种抗生素耐药菌株的出现。致病性金黄色葡萄球菌产生的几种毒素可引起严重的全身性感染，包括中毒性休克综合征毒素TSST-1和肠毒素B和c。最近，金黄色葡萄球菌毒素已成为一个特别关注的潜在生物恐怖主义制剂。噬菌体/致病性岛系统因其在转移毒素基因和赋予非致病性菌株致病性方面的作用而受到特别关注。

DESCRIPTION (provided by applicant): Staphylococcus aureus produces a number of toxins of great medical importance, including toxic shock syndrome toxin (TSST-1) and enterotoxins B and C. Several of these toxins are carried on so-called pathogenicity islands, genetic elements that resemble prophages, but do not carry most of the genes normally associated with phage activities. These elements are normally highly stable, but specific phages have the ability to excise them and package them into phage particles that can transfer the toxin genes to new cells. SaPI1 is an S. aureus pathogenicity island that carries the genes for TSST-1 as well as enterotoxins Q and L. SaPI1 is mobilized by phage 80?, and efficiently packaged into phage-like particles, using 80? structural proteins. However, the SaPI1 capsid is only 1/3 the size of the normal 80? capsid, commensurate with its smaller genome. It is not known what the mechanism of size determination is, but the system resembles the E. coli phage P2/P4 system, in which the satellite phage P4 hijacks the structural proteins from P2 and uses them to package a smaller capsid. The overall objective of this study is to understand the mechanism of size determination in the S. aureus phage 80?/Sal1 system and its role in the development of bacterial pathogenesis. In this study we will use cryo-electron microscopy and three-dimensional reconstruction methods to determine structures of phage 80? and SaPI1 particles. The specific aims of this study are: (1) Determine the 3D structure of S. aureus phage 80? capsids; (2) Determine the 3D structure of SaPI1 capsids; (3) Determine the structure of procapsids produced by co-expression of 80?/SaPI1 structural proteins. RELEVANCE TO PUBLIC HEALTH: Staphylococcus aureus has become a major health problem in hospitals, especially with the emergence of multiple antibiotic resistant strains. Several of the toxins produced by pathogenic S. aureus cause severe systemic infections, including the toxic shock syndrome toxin TSST-1 and enterotoxins B and C. Recently, S. aureus toxins have become a particular concern as potential bioterrorism agents. The bacteriophage/pathogenicity island system is of special interest for its role in transferring toxin genes and conferring pathogenicity on non-pathogenic strains.