Sequence-related protein export NTPases encoded by the conjugative transfer region of RP4 and by the cag pathogenicity island of Helicobacter pylori share similar hexameric ring structures.
Sequence-related protein export NTPases encoded by the conjugative transfer region of RP4 and by the cag pathogenicity island of Helicobacter pylori share similar hexameric ring structures.
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由 RP4 接合转移区和幽门螺杆菌 cag 致病性岛编码的序列相关蛋白输出 NTPase 具有相似的六聚环结构。
DOI：
10.1073/pnas.97.7.3067
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发表时间：
2000
影响因子：
11.1
通讯作者：
E. Lanka
中科院分区：
文献类型：
--
作者：
S. Krause;M. Bárcena;W. Pansegrau;R. Lurz;J. Carazo;E. Lanka
RP4 TrbB是广泛宿主质粒RP4共轭转移装置的重要组成部分，是PulE蛋白超家族的一员，参与跨细菌包膜运输大分子的多组分机制。pule样蛋白共享几个保守的基序，最显著的是一个核苷三磷酸结合基序（P-loop）。幽门螺杆菌HP0525也属于PulE超家族，由致病性岛cag编码，参与哺乳动物感染胃上皮细胞的炎症反应。经凝胶过滤和甘油梯度离心测定，TrbB和HP0525在ATP和Mg（2+）存在下呈同六聚体结构。在缺乏核苷酸和二价阳离子的情况下，TrbB表现为四聚体，而HP0525的六聚体状态不受影响。电镜和图像处理表明，TrbB和HP0525在ATP和Mg（2+）存在下形成环状配合物（直径12 nm），中心区域（直径3 nm）为低电子密度。然而，TrbB平均图像表现出更强的椭圆形，具有强的双重旋转对称性，而HP0525配合物是正六边形。在两种情况下，都可以区分出六个清晰的高电子密度三角形区域。TrbB的共价交联表明六聚环是由二聚体的三聚体组成的，因为只有二聚体、四聚体和六聚体可以检测到。TrbB和HP0525的环状结构表明，这两种蛋白质都催化了一个重复的过程，很可能是将同源底物转移到细胞膜上。
RP4 TrbB, an essential component of the conjugative transfer apparatus of the broad-host-range plasmid RP4, is a member of the PulE protein superfamily involved in multicomponent machineries transporting macromolecules across the bacterial envelope. PulE-like proteins share several well conserved motifs, most notable a nucleoside triphosphate binding motif (P-loop). Helicobacter pylori HP0525 also belongs to the PulE superfamily and is encoded by the pathogenicity island cag, involved in the inflammatory response of infected gastric epithelial cells in mammals. The native molecular masses of TrbB and HP0525 as determined by gel filtration and glycerol gradient centrifugation suggested a homohexameric structure in the presence of ATP and Mg(2+). In the absence of nucleotides and bivalent cations, TrbB behaved as a tetramer whereas the hexameric state of HP0525 remained unaffected. Electron microscopy and image processing demonstrated that TrbB and HP0525 form ring-shaped complexes (diameter: 12 nm) with a central region (diameter: 3 nm) of low electron density when incubated in the presence of ATP and Mg(2+). However, the TrbB average image appeared to be more elliptical with strong twofold rotational symmetry whereas HP0525 complexes are regular hexagons. Six well defined triangle-shaped areas of high electron density were distinguishable in both cases. Covalent crosslinking of TrbB suggests that the hexameric ring is composed from a trimer of dimers, because only dimeric, tetrameric, and hexameric species were detectable. The toroidal structure of TrbB and HP0525 suggests that both proteins catalyze a repetitive process, most probably translocating a cognate substrate across the inner membrane.