The legume Rhizobium symbiosis leads to the formation of a new compartment in the plant cell, the symbiosome. This compartment harbours the bacteroids surrounded by a peribacteroid membrane (PBM) originating from the plant plasma membrane. The PBM and the space between the PBM and the bacteroid membrane, called peribacteroid space (PS), mediate the exchange of metabolites between the symbionts. Proteome analysis was used as an approach to characterise the proteins in the PBM and the PS. A standard differential centrifugation procedure including a Percoll gradient was used for symbiosome isolation from pea root nodules. Proteins in the PBM and PS fractions obtained from the symbiosomes were separated by two-dimensional gel electrophoresis, and 89 spots were analysed by tandem mass spectrometry. The proteins of 46 spots could be identified by database search. The results showed that PS and even PBM preparations from pea symbiosomes always contain abundant amounts of bacteroid proteins as a contaminate. Interestingly, in addition to a few PS/PBM proteins a number of endomembrane proteins (less likely representing a contaminate), including V-ATPase, BIP, and an integral membrane protein known from COPI-coated vesicles, were found in the PBM fraction, supporting the role of the endomembrane system in PBM biogenesis.

中文翻译：

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豌豆（Pisum sativum）共生体的菌周空间和菌周膜制剂的蛋白质组学表征。


豆科植物根瘤菌共生导致植物细胞中新的隔室（共生体）的形成。该隔室包含由源自植物质膜的类菌周膜（PBM）包围的类菌体。 PBM 以及 PBM 和类菌膜之间的空间（称为类菌周空间 (PS)）介导共生体之间代谢物的交换。蛋白质组分析被用作表征 PBM 和 PS 中蛋白质的方法。使用包括 Percoll 梯度的标准差速离心程序从豌豆根瘤中分离共生体。通过二维凝胶电泳分离从共生体获得的 PBM 和 PS 级分中的蛋白质，并通过串联质谱分析 89 个点。通过数据库检索可鉴定出46个位点的蛋白质。结果表明，来自豌豆共生体的 PS 甚至 PBM 制剂始终含有大量的类菌蛋白作为污染物。有趣的是，除了一些 PS/PBM 蛋白外，在 PBM 组分中还发现了许多内膜蛋白（不太可能代表污染物），包括 V-ATP 酶、BIP 和 COPI 包被囊泡中已知的完整膜蛋白，支持内膜系统在 PBM 生物发生中的作用。