Biogenesis of Gas Vesicles in Halobacterium

9809906StuartGas囊泡是许多水生原核生物产生的独特细胞器，可能用于浮选。它们被一层异常稳定的蛋白质膜包裹着一个充满气体的空间。自1888年Winogradsky发现以来，虽然在代表古细菌和真细菌的许多原核生物物种中发现了它们，但小泡的一般形态看起来非常相似，至少主要蛋白质看起来是同源的。多年来，研究人员假设气泡是由单一的自结合蛋白形成的。然而，DasSarma和他的同事最近的分子遗传学工作，使用古细菌原核生物盐杆菌作为他们的模式系统，导致发现了一大群与气泡形成有关的基因。此外，他们能够将基因簇转移到大肠杆菌的实验室菌株中，并在这种细菌中设计气泡的表达，这种细菌自然不会产生气泡。DasSarma和他的同事们正在继续他们关于嗜盐杆菌气泡生物发生的工作，使用免疫学和分子遗传学的方法来分析蛋白质形成、组装和调节过程中的序列和时间，以构建功能气泡。单个蛋白质要用免疫学程序标记，然后用免疫金细胞学方法定位在有机体内。盐杆菌的突变菌株也将被研究，以确定导致囊泡形成的基因激活和作用序列。与突变体和纯化蛋白产物的互补研究将有助于理解蛋白质相互作用在构建囊泡膜过程中的动力学。总体目标是描述气泡生物发生中的组成蛋白和调控信号，并了解导致它们形成的遗传和代谢事件的顺序

9809906StuartGas vesicles are unique organelles produced by many aquatic prokaryotic microorganisms and used presumably for flotation. They are bounded by an unusually stable proteinaceous membrane that enfolds a gas filled space. Although detected in numerous groups of prokaryotic species representing both archaea and true bacteria since their discovery in 1888 by Winogradsky, the general morphology of the vesicles appears very similar and at least the major proteins appear homologous. For many years, researchers hypothesized that gas vesicles were formed from a single self-associating protein. However, recent molecular genetic work by DasSarma and his colleagues, using the archaeal prokaryote Halobacterium as their model system, led to the discovery of a large cluster of genes involved in gas vesicle formation. Further, they were able to transfer the gene cluster to laboratory strains of E. coli and engineer the expression of gas vesicles in this bacterium, which does not naturally produce gas vesicles. The gene cluster is hypothesized to comprise three genes coding for structural proteins, in rightward transcriptional orientation, and ten or more genes encoding regulatory or initiation proteins, in leftward transcriptional orientation.DasSarma and his colleagues are continuing their work on biogenesis of gas vesicles in Halobacterium, using immunological and molecular-genetic methods to analyze the sequence and timing of steps in protein formation, assembly, and regulation to build functional gas vesicles. Individual proteins are to be tagged using immunological procedures, and then localized within the organism using immunogold cytological nethods. Mutants strains of Halobacterium will also be studied to determine the sequence of gene activation and action leading to vesicle formation. Complementation studies with mutants and purified protein products will help understand the dynamics of protein interactions in building the vesicle membrane. The overall goal is to describe the component proteins and regulatory signals in the biogenesis of gas vesicles and understand the sequence of genetic and metabolic events leading to their formation