Secretion of immunodominant membrane protein from onion yellows phytoplasma through the Sec protein-translocation system in Escherichia coli
Secretion of immunodominant membrane protein from onion yellows phytoplasma through the Sec protein-translocation system in Escherichia coli
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DOI：
10.1099/mic.0.26521-0
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发表时间：
2004-01-01
期刊：
影响因子：
2.8
通讯作者：
Namba, S
中科院分区：
文献类型：
--
作者：
Kakizawa, S;Oshima, K;Namba, S
从洋葱黄化植原体（OY）中克隆了一个编码假定SecE蛋白的基因，该蛋白是Sec蛋白易位系统的一个组成部分。该基因的鉴定和以前报道的SecA和SecY基因的编码提供了证据，Sec系统存在于植原体。另外，还克隆了编码OY的抗原性膜蛋白（antigenic membrane protein，EMP3）（一种免疫显性膜蛋白）的基因，并进行了序列测定。OY amp基因全长702 nt，编码233个氨基酸的蛋白质。与紫菀黄化植原体（AY）高度相似。在大肠杆菌中过表达部分OY β，纯化，并用于产生抗β的多克隆抗体。在Western印迹分析中，抗OY抗体与OY感染的植物提取物特异性反应，因此可用于检测OY和OY。它具有一个保守的蛋白基序，已知该基序由大肠杆菌的Sec系统输出。在大肠杆菌中表达的部分OY β蛋白定位于周质中，作为蛋白质的较短的、pupely-processed形式。它可能是通过Sec系统从细胞质输出到周质的。此外，在OY中表达并在OY感染的植物中检测到的OY β蛋白显然也被加工。由于植原体不能培养或转化，关于其蛋白质分泌系统的信息很少。这项研究表明，SEC系统在这种植原体输出OY的植物。
A gene that encodes a putative SecE protein, which is a component of the Sec protein-translocation system, was cloned from the onion yellows phytoplasma (OY). The identification of this gene and the previously reported genes encoding SecA and SecY provides evidence that the Sec system exists in phytoplasma. In addition, a gene encoding an antigenic membrane protein (Amp) (a type of immunodominant membrane protein) of OY was cloned and sequenced. The OY amp gene consisted of 702 nt encoding a protein of 233 aa. which was highly similar to Amp of aster yellows phytoplasma (AY). Part of OY Amp was overexpressed in Escherichia coli, purified, and used to raise an anti-Amp polyclonal antibody. The anti-Amp antibody reacted specifically with an OY-infected plant extract in Western blot analysis and was therefore useful for the detection of OY as well as Amp. Amp has a conserved protein motif that is known to be exported by the Sec system of E coli. A partial OY Amp protein expressed in E coli was localized in the periplasm as a shorter, putatively processed form of the protein. It had probably been exported from the cytoplasm to the periplasm through the Sec system. Moreover, OY Amp protein expressed in OY and detected in OY-infected plants was apparently also processed. Because phytoplasmas cannot be cultured or transformed, little information is available regarding their protein secretion systems. This study suggests that the Sec system operates in this phytoplasma to export OY Amp.