The Predicted Lytic Transglycosylase HpaH from Xanthomonas campestris pv. vesicatoria Associates with the Type III Secretion System and Promotes Effector Protein Translocation
The Predicted Lytic Transglycosylase HpaH from Xanthomonas campestris pv. vesicatoria Associates with the Type III Secretion System and Promotes Effector Protein Translocation
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DOI：
10.1128/iai.00788-16
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发表时间：
2017-02-01
影响因子：
3.1
通讯作者：
Buettner, Daniela
中科院分区：
文献类型：
--
作者：
Hausner, Jens;Hartmann, Nadine;Buettner, Daniela
研究了一种革兰氏阴性植物病原细菌野油菜黄单胞菌致病性。vesicatoria依赖于III型分泌（T3 S）系统，其跨越细菌膜并将效应蛋白易位到植物细胞中。T3 S系统的组装可能涉及预测的裂解转糖基酶（LT）HpaH，其邻近T3 S基因簇编码。细菌LT降解肽聚糖，通常促进跨膜大分子蛋白质复合物的形成。在本研究中，我们表明，HpaH定位于细菌周质和结合肽聚糖以及T3 S系统的组件，包括预测的周质内杆蛋白HrpB 1和HrpB 2以及菌毛蛋白HrpE。体内易位试验表明，HpaH促进易位的各种效应蛋白和T3 S系统的早期底物，这表明HpaH的III型依赖的蛋白质出口的一般贡献。突变体研究和报告融合体分析表明，HpaH的N末端区域有助于蛋白质功能，并且被蛋白水解切割。N-末端截短的HpaH裂解产物通过一种未知的转运途径分泌到细胞外环境中，该途径不依赖于T3 S系统。
The pathogenicity of the Gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system, which spans both bacterial membranes and translocates effector proteins into plant cells. The assembly of the T3S system presumably involves the predicted lytic transglycosylase (LT) HpaH, which is encoded adjacent to the T3S gene cluster. Bacterial LTs degrade peptidoglycan and often promote the formation of membrane-spanning macromolecular protein complexes. In the present study, we show that HpaH localizes to the bacterial periplasm and binds to peptidoglycan as well as to components of the T3S system, including the predicted periplasmic inner rod proteins HrpB1 and HrpB2 as well as the pilus protein HrpE. In vivo translocation assays revealed that HpaH promotes the translocation of various effector proteins and of early substrates of the T3S system, suggesting a general contribution of HpaH to type III-dependent protein export. Mutant studies and the analysis of reporter fusions showed that the N-terminal region of HpaH contributes to protein function and is proteolytically cleaved. The N-terminally truncated HpaH cleavage product is secreted into the extracellular milieu by a yet-unknown transport pathway, which is independent of the T3S system.