Institute for Genome Sciences and Policy, Duke University, Durham, North Carolina 27708, USA.
J Proteome Res. 2013 Feb 1;12(2):704-18. doi: 10.1021/pr3007842. Epub 2012 Dec 27.
Many insect groups have coevolved with bacterial endosymbionts that live within specialized host cells. As a salient example, ants in the tribe Camponotini rely on Blochmannia, an intracellular bacterial mutualist that synthesizes amino acids and recycles nitrogen for the host. We performed a shotgun, label-free, LC/MS/MS quantitative proteomic analysis to investigate the proteome of Blochmannia associated with Camponotus chromaiodes. We identified more than 330 Blochmannia proteins, or 54% coverage of the predicted proteome, as well as 244 Camponotus proteins. Using the average intensity of the top 3 "best flier" peptides along with spiking of a surrogate standard at a known concentration, we estimated the concentration (fmol/μg) of those proteins with confident identification. The estimated dynamic range of Blochmannia protein abundance spanned 3 orders of magnitude and covered diverse functional categories, with particularly high representation of metabolism, information transfer, and chaperones. GroEL, the most abundant protein, totaled 6% of Blochmannia protein abundance. Biosynthesis of essential amino acids, fatty acids, and nucleotides, and sulfate assimilation had disproportionately high coverage in the proteome, further supporting a nutritional role of the symbiosis. This first quantitative proteomic analysis of an ant endosymbiont illustrates a promising approach to study the functional basis of intimate symbioses.
许多昆虫群体与生活在专门宿主细胞内的细菌内共生体共同进化。作为一个突出的例子，Camponotini 蚂蚁依赖于 Blochmannia，这是一种为宿主合成氨基酸和回收氮的细胞内细菌共生体。我们进行了一种无标记、鸟枪法、LC/MS/MS 定量蛋白质组学分析，以研究与 Camponotus chromaiodes 相关的 Blochmannia 蛋白质组。我们鉴定了 330 多种 Blochmannia 蛋白，或预测蛋白质组的 54%覆盖率，以及 244 种 Camponotus 蛋白。使用前 3 个“最佳飞行者”肽的平均强度以及以已知浓度添加的替代标准品，可以估计具有可靠鉴定的那些蛋白质的浓度（fmol/μg）。Blochmannia 蛋白丰度的估计动态范围跨越 3 个数量级，涵盖了多种功能类别，其中代谢、信息传递和伴侣蛋白的代表性特别高。GroEL 是最丰富的蛋白质，占 Blochmannia 蛋白丰度的 6%。必需氨基酸、脂肪酸和核苷酸的生物合成以及硫酸盐同化在蛋白质组中具有不成比例的高覆盖率，进一步支持了共生体的营养作用。这是对蚂蚁内共生体的第一次定量蛋白质组学分析，为研究密切共生的功能基础提供了一种有前途的方法。
