Characterization of the exosporium basal layer protein BxpB of Bacillus anthracis
Characterization of the exosporium basal layer protein BxpB of Bacillus anthracis
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DOI：
10.1128/jb.187.17.5868-5876.2005
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发表时间：
2005-09-01
影响因子：
3.2
通讯作者：
Turnbough, CL
中科院分区：
文献类型：
--
作者：
Steichen, CT;Kearney, JF;Turnbough, CL
炭疽芽孢杆菌的孢子是炭疽病的病原，它被一个叫做外孢壁的突出的松散结构所包围。外孢壁由基底层和外部毛状绒毛组成。毛发状绒毛的细丝显然是由一种称为BclA的胶原样糖蛋白形成的，而几种不同的蛋白质形成或与基底层紧密相关。在这项研究中，我们使用免疫金电子显微镜来证明BxpB（也称为ExsF）是外孢壁基底层的一个组成部分。BclA的丧失大大增加了抗BxpB单克隆抗体与基底层的结合。我们发现，BxpB和BctA是一个稳定的复合物，似乎包括推定的基底层蛋白ExsY和可能的其他蛋白质的一部分。先前的结果表明BxpB是糖基化的，然而，我们的结果表明它不是糖蛋白。我们发现，Delta bxpB孢子，缺乏BxpB，含有外孢壁缺乏头发样绒毛，即使Delta bxpB菌株产生正常水平的BclA。这些结果表明BxpB是BclA附着于外孢壁所必需的。最后，我们发现Delta bxpB孢子的生产效率和它们的抗性特性与野生型孢子相似。然而，Delta bxpB孢子比野生型孢子萌发更快，表明BxpB抑制萌发。这种效果似乎并没有涉及到从三角洲bxpB孢子的头发样的午睡或降解发芽酶的情况下。
Bacillus anthracis spores, the cause of anthrax, are enclosed by a prominent loose-fitting structure called the exosporium. The exosporium is composed of a basal layer and an external hair-like nap. The filaments of the hair-like nap are apparently formed by a single collagen-like glycoprotein called BclA, whereas several different proteins form or are tightly associated with the basal layer. In this study, we used immunogold electron microscopy to demonstrate that BxpB (also called ExsF) is a component of the exosporium basal layer. Binding to the basal layer by an anti-BxpB monoclonal antibody was greatly increased by the loss of BclA. We found that BxpB and BctA are part of a stable complex that appears to include the putative basal layer protein ExsY and possibly other proteins. Previous results suggested that BxpB was glycosylated; however, our results indicate that it is not a glycoprotein. We showed that Delta bxpB spores, which lack BxpB, contain an exosporium devoid of hair-like nap even though the Delta bxpB strain produces normal levels of BclA. These results indicated that BxpB is required for the attachment of BclA to the exosporium. Finally, we found that the efficiency of production of Delta bxpB spores and their resistance properties were similar to those of wild-type spores. However, Delta bxpB spores germinate faster than wild-type spores, indicating that BxpB suppresses germination. This effect did not appear to be related to the absence from Delta bxpB spores of a hair-like nap or of enzymes that degrade germinants.