The ShdA adhesin binds to the cationic cradle of the fibronectin 13FnIII repeat module:: evidence for molecular mimicry of heparin binding
The ShdA adhesin binds to the cationic cradle of the fibronectin 13FnIII repeat module:: evidence for molecular mimicry of heparin binding
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DOI：
10.1111/j.1365-2958.2004.03995.x
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发表时间：
2004-04-01
影响因子：
3.6
通讯作者：
Bäumler, AJ
中科院分区：
文献类型：
--
作者：
Kingsley, RA;Keestra, AM;Bäumler, AJ
将肠道沙门氏菌血清型鼠伤寒沙门氏菌引入食品中是由于其能够通过尚不清楚的机制在健康牲畜的肠道中持续存在。非菌毛粘附素ShdA是一种纤维连接蛋白结合蛋白，是肠内持续携带链球菌所必需的。鼠伤寒。我们进一步研究了ShdA介导的肠持久性的分子机制，通过确定该受体在纤维连接蛋白中的结合位点。ShdA与纤连蛋白蛋白水解片段和重组纤连蛋白融合蛋白结合的分析鉴定了Hep-2结构域的（13）FnIII重复模块作为该粘附素的主要结合位点。纤连蛋白的（13）FnIII重复模块包含由六个碱性残基（R6、R7、R9、R23、K25和R54）形成的阳离子摇篮，其是在从青蛙到人的纤连蛋白序列中保守的高亲和力肝素结合位点。此外，ShdA的Hep-2结构域的结合是敏感的离子缓冲强度，这表明结合涉及离子相互作用。因此，我们确定了抑制肝素结合的Hep-2结构域阳离子摇篮中的碱性残基的氨基酸取代是否也废除了ShdA的结合。R6 S和R7S的组合取代强烈降低了ShdA与（13）FnIII的结合。这些数据表明，ShdA结合的Hep-2结构域的纤连蛋白的机制，可以模仿结合的主机多糖肝素。
Introduction of Salmonella enterica serotype Typhimurium into food products results from its ability to persist in the intestine of healthy livestock by mechanisms that are poorly understood. The non-fimbrial adhesin ShdA is a fibronectin binding protein required for persistent intestinal carriage of S. Typhimurium. We further investigated the molecular mechanism of ShdA-mediated intestinal persistence by determining the binding-site of this receptor in fibronectin. Analysis of ShdA binding to fibronectin proteolytic fragments and to recombinant fibronectin fusion proteins identified the (13)FnIII repeat module of the Hep-2 domain as the primary binding site for this adhesin. The (13)FnIII repeat module of fibronectin contains a cationic cradle formed by six basic residues (R6, R7, R9, R23, K25 and R54) that is a high affinity heparin-binding site conserved among fibronectin sequences from frogs to man. Binding of ShdA to the (13)FnIII repeat module of fibronectin and to a second extracellular matrix protein, Collagen I, could be inhibited by heparin. Furthermore, binding of ShdA to the Hep-2 domain was sensitive to the ionic buffer strength, suggesting that binding involved ionic interactions. We therefore determined whether amino acid substitutions of basic residues in the cationic cradle of the Hep-2 domain that inhibit heparin binding also abrogate binding of ShdA. Combined substitution of R6S and R7S strongly reduced ShdA binding to (13)FnIII. These data suggest that ShdA binds the Hep-2 domain of fibronectin by a mechanism that may mimic binding of the host polysaccharide heparin.