Biological role of outer membrane vesicle-associated small proteins of the phytopathogen Agrobacterium tumefaciens

细菌细胞外膜囊泡被认为是各种细胞通讯系统中的新参与者。外膜囊泡(OMV)是许多革兰氏阴性菌的外膜释放出来的。这些胞外纳米结构的货物包括不同的生物分子，如小化合物、遗传物质、蛋白质和多肽，这些分子参与物种内和物种间的沟通和致病。我们最近证明，引起冠癌的植物病原体根癌农杆菌在生长过程中将OMV释放到培养上清液中。对不同生长条件下获得的OMV组分进行蛋白质组学研究，鉴定出约60个蛋白质，其中包括功能未知的两个保守的小蛋白Atu2614和Atu8019。这两种蛋白质都含有一个预测的N-末端信号肽II序列和一个C-末端共有脂盒，这是脂蛋白的一个标志。Atu2614的成熟形式预计包含67个氨基酸，并包含一个高度疏水的结构域，其中有几个扩展的甘氨酸拉链基序，这些基序通常存在于成孔膜蛋白中。Atu8019(成熟大小：32个氨基酸)与肠毒素解毒剂/毒素肽有相似的序列。在本研究中，我们旨在通过结合遗传和生化方法来阐明这两个OMV相关小蛋白在农杆菌中的生物学作用。通过这些研究，我们希望对OMV相关的小脂蛋白在细菌中的生理相关性获得新的有价值的见解。

Bacterial extracellular membrane vesicles are considered as novel players in various cell communication systems. Outer membrane vesicles (OMVs) are released from the outer membrane of many Gram-negative bacteria. The cargo of these extracellular nanostructures comprises distinct biomolecules such as small compounds, genetic material, proteins and peptides, which are involved in intra- and inter-species communication and pathogenicity.We have recently demonstrated that the phytopathogen Agrobacterium tumefaciens, the causative agent of crown gall disease, releases OMVs into the culture supernatant during growth. A proteome study of the OMV fractions obtained under different growth conditions identified about 60 proteins including the two conserved small proteins Atu2614 and Atu8019 with unknown functions. Both proteins contain a predicted N-terminal signal peptidase II sequence with a C-terminal consensus lipobox, a hallmark of lipoproteins. The mature form of Atu2614 is expected to contain 67 aa and comprises a highly hydrophobic domain with several extended glycine-zipper motifs commonly found in pore-forming membrane proteins. Atu8019 (mature size: 32 aa) shares sequence similarities to entericidin antidote/toxin peptides.In this proposal we aim at elucidating the biological roles of these two OMV-associated small proteins in Agrobacterium by combining genetic and biochemical approaches. With these studies we expect to obtain new valuable insights into the physiological relevance of OMV-associated small lipoproteins in bacteria.