The Periplasmic HrpB1 Protein from Xanthomonas spp. Binds to Peptidoglycan and to Components of the Type III Secretion System
The Periplasmic HrpB1 Protein from Xanthomonas spp. Binds to Peptidoglycan and to Components of the Type III Secretion System
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DOI：
10.1128/aem.01226-13
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发表时间：
2013-10-01
影响因子：
4.4
通讯作者：
Buettner, Daniela
中科院分区：
文献类型：
--
作者：
Hausner, Jens;Hartmann, Nadine;Buettner, Daniela
植物病原细菌野油菜黄单胞菌致病变种（Xanthomonascampestris pv.）vesicatoria利用III型分泌（T3 S）系统将细菌效应蛋白易位到真核宿主细胞中。跨膜分泌器由11个核心组分和几个功能未知的相关蛋白组成。在这项研究中，我们分析了HrpB 1的作用，这是以前被证明是必不可少的T3 S和细胞外T3 S菌毛的形成。我们提供的实验证据表明，HrpB 1定位于细菌周质和结合肽聚糖，这是在协议与其预测的结构相似性推定的肽聚糖结合域的裂解转糖基酶Slt 70从大肠杆菌。相互作用的研究表明，HrpB 1形成蛋白复合物，并结合到T3 S系统的组件，包括内膜蛋白HrcD，分泌素HrcC，菌毛蛋白HrpE，和推定的内杆蛋白HrpB 2。HrpB 1的缺失和点突变衍生物的分析导致鉴定有助于HrpB 1与其自身和HrcD和/或蛋白质功能的相互作用的氨基酸残基。HrpB 1和HrpB 2共定位于周质，并与HrcD相互作用，这一发现表明它们是T3 S系统周质亚结构的一部分。
The plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria employs a type III secretion (T3S) system to translocate bacterial effector proteins into eukaryotic host cells. The membrane-spanning secretion apparatus consists of 11 core components and several associated proteins with yet unknown functions. In this study, we analyzed the role of HrpB1, which was previously shown to be essential for T3S and the formation of the extracellular T3S pilus. We provide experimental evidence that HrpB1 localizes to the bacterial periplasm and binds to peptidoglycan, which is in agreement with its predicted structural similarity to the putative peptidoglycan-binding domain of the lytic transglycosylase Slt70 from Escherichia coli. Interaction studies revealed that HrpB1 forms protein complexes and binds to T3S system components, including the inner membrane protein HrcD, the secretin HrcC, the pilus protein HrpE, and the putative inner rod protein HrpB2. The analysis of deletion and point mutant derivatives of HrpB1 led to the identification of amino acid residues that contribute to the interaction of HrpB1 with itself and HrcD and/or to protein function. The finding that HrpB1 and HrpB2 colocalize to the periplasm and both interact with HrcD suggests that they are part of a periplasmic substructure of the T3S system.