From the Department of Chemistry, California State University, Fresno, California 93740.
From the Department of Chemistry, California State University, Fresno, California 93740
J Biol Chem. 2018 Aug 31;293(35):13626-13635. doi: 10.1074/jbc.RA118.003888. Epub 2018 Jul 5.
causes listeriosis, a potentially fatal food-borne disease. The condition is especially harmful to pregnant women. outbreaks can originate from diverse foods, highlighting the need for novel strategies to improve food safety. The first step in invasion is internalization of the bacteria, which is mediated by the interaction of the internalin family of virulence factors with host cell receptors. A crucial interaction for invasion of the placenta, and thus a target for therapeutic intervention, is between internalin B (InlB) and the receptor c-Met. Single-domain antibodies (VH, also called nanobodies, or sdAbs) from camel heavy-chain antibodies are a novel solution for preventing infections. The VH R303, R330, and R326 all bind InlB with high affinity; however, the molecular mechanism behind their mode of action was unknown. We demonstrate that despite a high degree of sequence and structural diversity, the VH bind a single epitope on InlB. A combination of gentamicin protection assays and florescent microscopy establish that InlB-specific VH inhibit invasion of HeLa cells. A high-resolution X-ray structure of VH R303 in complex with InlB showed that the VH binds at the c-Met interaction site on InlB, thereby acting as a competitive inhibitor preventing bacterial invasion. These results point to the potential of VH as a novel class of therapeutics for the prevention of listeriosis.
李斯特菌会引起李斯特菌病，这是一种潜在致命的食源性疾病。这种疾病对孕妇尤其有害。疫情可能源自各种不同的食物，这突显了需要新的策略来提高食品安全。细菌内化是李斯特菌入侵的第一步，这是由毒力因子的内毒素家族与宿主细胞受体相互作用介导的。在胎盘入侵中，内毒素 B (InlB) 与受体 c-Met 之间的相互作用是至关重要的，这也是治疗干预的目标。来自骆驼重链抗体的单域抗体 (VH，也称为纳米抗体或 sdAb) 是预防李斯特菌感染的一种新方法。VH R303、R330 和 R326 与 InlB 结合的亲和力都很高；然而，它们作用模式的分子机制尚不清楚。我们证明，尽管 VH 具有高度的序列和结构多样性，但它们结合 InlB 的单一表位。庆大霉素保护试验和荧光显微镜的组合表明，InlB 特异性 VH 抑制 HeLa 细胞的入侵。VH R303 与 InlB 复合物的高分辨率 X 射线结构表明，VH 结合 InlB 上的 c-Met 相互作用位点，从而作为竞争性抑制剂阻止细菌入侵。这些结果表明 VH 有可能成为预防李斯特菌病的一类新型治疗药物。
