Yeo Hye-Jeong, Yokoyama Takeshi, Walkiewicz Katarzyna, Kim Youngchang, Grass Susan, Geme Joseph W St
Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204, USA.
J Biol Chem. 2007 Oct 19;282(42):31076-84. doi: 10.1074/jbc.M705750200. Epub 2007 Aug 14.
In pathogenic Gram-negative bacteria, many virulence factors are secreted via the two-partner secretion pathway, which consists of an exoprotein called TpsA and a cognate outer membrane translocator called TpsB. The HMW1 and HMW2 adhesins are major virulence factors in nontypeable Haemophilus influenzae and are prototype two-partner secretion pathway exoproteins. A key step in the delivery of HMW1 and HMW2 to the bacterial surface involves targeting to the HMW1B and HMW2B outer membrane translocators by an N-terminal region called the secretion domain. Here we present the crystal structure at 1.92 A of the HMW1 pro-piece (HMW1-PP), a region that contains the HMW1 secretion domain and is cleaved and released during HMW1 secretion. Structural analysis of HMW1-PP revealed a right-handed beta-helix fold containing 12 complete parallel coils and one large extra-helical domain. Comparison of HMW1-PP and the Bordetella pertussis FHA secretion domain (Fha30) reveals limited amino acid homology but shared structural features, suggesting that diverse TpsA proteins have a common structural domain required for targeting to cognate TpsB proteins. Further comparison of HMW1-PP and Fha30 structures may provide insights into the keen specificity of TpsA-TpsB interactions.
在致病性革兰氏阴性菌中，许多毒力因子通过双组分分泌途径分泌，该途径由一种名为TpsA的外蛋白和一种与之对应的名为TpsB的外膜转运蛋白组成。高分子量1型（HMW1）和高分子量2型（HMW2）黏附素是不可分型流感嗜血杆菌的主要毒力因子，是双组分分泌途径外蛋白的典型代表。将HMW1和HMW2递送至细菌表面的关键步骤涉及通过一个名为分泌结构域的N端区域靶向HMW1B和HMW2B外膜转运蛋白。在此，我们展示了HMW1前体片段（HMW1-PP）的1.92 Å晶体结构，该区域包含HMW1分泌结构域，且在HMW1分泌过程中被切割并释放。对HMW1-PP的结构分析揭示了一种右手β-螺旋折叠，包含12个完整的平行螺旋圈和一个大的螺旋外结构域。对HMW1-PP和百日咳博德特氏菌丝状血凝素分泌结构域（Fha30）的比较显示，氨基酸同源性有限，但结构特征相同，这表明不同的TpsA蛋白具有一个靶向其对应的TpsB蛋白所需的共同结构域。对HMW1-PP和Fha30结构的进一步比较可能会为TpsA-TpsB相互作用的高度特异性提供见解。
