Hrtska Sybil C Lang, Kemp Melissa M, Muñoz Eva M, Azizad Omaira, Banerjee Mani, Raposo Catarina, Kumaran Jyothi, Ghosh Partho, Linhardt Robert J
Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa 52242, USA.
Biochemistry. 2007 Mar 13;46(10):2697-706. doi: 10.1021/bi062021x. Epub 2007 Feb 17.
Listeria monocytogenes, a food-borne pathogen that infects immunocompromised patients, enters and proliferates within mammalian cells by taking advantage of host cell machinery. While entry into macrophages and other phagocytic cells occurs constitutively, intracellular invasion of nonphagocytic cells, such as epithelial and endothelial cells, occurs through induced phagocytosis. Invasion of these nonphagocytic cell types is under the control of the secreted L. monocytogenes protein internalin B (InlB), which directly associates with and activates the receptor tyrosine kinase Met. Activation of Met by InlB has previously been shown to be potentiated by binding of glycosaminoglycans to the GW domains of this protein. We studied the interaction between heparin and full-length InlB as well as a truncated, functional form of InlB to understand the mode of interaction between these two molecules. InlB preferred long-chain (>or=dp14) heparin oligosaccharides, and the interaction with heparin fit a complicated binding model with a dissociation constant in the nanomolar range. While there are various explanations for this complicated binding model, one supported by our data involves binding and rebinding of InlB to multiple binding sites on heparin in a positive and weakly cooperative manner. This mode is consistent with enhancement of interaction of InlB with glycosaminoglycans for activation of Met.
单核细胞增生李斯特菌是一种食源性病原体，可感染免疫功能低下的患者，它利用宿主细胞机制在哺乳动物细胞内进入并增殖。虽然它可组成性地进入巨噬细胞和其他吞噬细胞，但它通过诱导吞噬作用进入非吞噬细胞，如上皮细胞和内皮细胞，并在其中进行细胞内侵袭。这些非吞噬细胞类型的侵袭受分泌的单核细胞增生李斯特菌内化素B（InlB）的控制，InlB可直接与受体酪氨酸激酶Met结合并激活它。此前已表明，糖胺聚糖与该蛋白的GW结构域结合可增强InlB对Met的激活作用。我们研究了肝素与全长InlB以及截短的功能性InlB之间的相互作用，以了解这两种分子之间的相互作用模式。InlB更倾向于长链（≥dp14）肝素寡糖，并且与肝素的相互作用符合一个复杂的结合模型，解离常数在纳摩尔范围内。虽然对于这个复杂的结合模型有各种解释，但我们的数据支持的一种解释是，InlB以正向且弱协同的方式与肝素上的多个结合位点结合和解离。这种模式与增强InlB与糖胺聚糖的相互作用以激活Met是一致的。
