The Bactericidal Activity of the C-type Lectin RegIIIβ against Gram-negative Bacteria involves Binding to Lipid A
The Bactericidal Activity of the C-type Lectin RegIIIβ against Gram-negative Bacteria involves Binding to Lipid A
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DOI：
10.1074/jbc.m112.399998
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发表时间：
2012-10-05
影响因子：
4.8
通讯作者：
Hardt, Wolf-Dietrich
中科院分区：
文献类型：
--
作者：
Miki, Tsuyoshi;Holst, Otto;Hardt, Wolf-Dietrich
RegIII beta是C型凝集素家族的成员，称为RegIII。已知其结合肽聚糖，并且其杀菌活性形成与肠道细菌和致病性肠道细菌的相互作用。然而，很少有人知道它的碳水化合物识别特异性和杀菌机制，特别是对革兰氏阴性菌。在这里，我们表明，RegIII β可以通过识别脂质A的碳水化合物部分，通过一个新的基序，这是其杀菌活性不可或缺的直接结合到LPS。RegIII β的杀菌活性可通过与LPS、脂质A或龙胆二糖预孵育来抑制。后者是一种由两个β-（1 -> 6）连接的D-葡萄糖单元组成的二糖，类似于脂质A的碳水化合物部分。因此，该结构元件可形成RegIII β识别的关键靶位点。使用点突变的RegIII β蛋白，我们发现称为“环1”和“环2”的两个结构基序中的氨基酸残基对于肽聚糖和脂质A结合（Arg-135，Asp-142）以及杀菌活性（Glu-134，Asn-136，Asp-142）是重要的。因此，环2中的ERN基序和残基Asp-142对于RegIII β功能至关重要。这为RegIII β的碳水化合物识别特异性提供了新的见解，并解释了其对革兰氏阴性菌的杀菌活性。
RegIII beta is a member of the C-type lectin family called RegIII. It is known to bind peptidoglycan, and its bactericidal activity shapes the interactions with commensal and pathogenic gut bacteria. However, little is known about its carbohydrate recognition specificity and the bactericidal mechanism, particularly against Gram-negative bacteria. Here, we show that RegIII beta can bind directly to LPS by recognizing the carbohydrate moiety of lipid A via a novel motif that is indispensable for its bactericidal activity. This bactericidal activity of RegIII beta could be inhibited by preincubation with LPS, lipid A, or gentiobiose. The latter is a disaccharide composed of two units of beta-(1 -> 6)-linked D-glucose and resembles the carbohydrate moiety of lipid A. Therefore, this structural element may form a key target site recognized by RegIII beta. Using point-mutated RegIII beta proteins, we found that amino acid residues in two structural motifs termed "loop 1" and "loop 2," are important for peptidoglycan and lipid A binding (Arg-135, Asp-142) and for the bactericidal activity (Glu-134, Asn-136, Asp-142). Thus, the ERN motif and residue Asp-142 in the loop 2 are of critical importance for RegIII beta function. This provides novel insights into the carbohydrate recognition specificity of RegIII beta and explains its bactericidal activity against Gram-negative bacteria.