胃幽門螺旋桿菌被認為是最常見的感染源，幾乎有一半以上的人口都感染有胃幽門螺旋桿菌。近來發現，有一種胃幽門螺旋桿菌的蛋白會高度引起人體的免疫反應，此蛋白被稱為嗜中性白血球激活蛋白。然而，直接從胃幽門螺旋桿菌中純化出嗜中性白血球激活蛋白是非常困難的，因為胃幽門螺旋桿菌一定要生長在微厭氧的環境下，而且產量也不多。迄今，沒有報導指出可以從大腸桿菌的表達系統中得到具有功能的重組嗜中性白血球激活蛋白。為了確定是否可以從大腸桿菌的表達系統中得到具有功能且由十二個單體所組成的嗜中性白血球激活蛋白，從大腸桿菌表達系統中被純化出的重組自然嗜中性白血球激活蛋白和帶有六個組胺酸的嗜中性白血球激活蛋白進一步地被定性。經由超高速離心與凝膠過濾之分析，重組自然嗜中性白血球激活蛋白和帶有六個組胺酸的嗜中性白血球激活蛋白呈現多體聚合的情況。利用旋光儀分析，確定了純化出來的重組蛋白都具有a-螺旋狀的二級結構。同時，經由化學冷光與西方墨點法，證明純化出來的重組蛋白能使細胞產生過氧化物並增加ERK的磷酸化。從此一大腸桿菌的表達系統中，可以純化得到大量的重組嗜中性白血球激活蛋白。而重組的嗜中性白血球激活蛋白之多聚體與活性都與從胃幽門螺旋桿菌來的嗜中性白血球激活蛋白相似。此結果證明著從大腸桿菌純化來的重組嗜中性白血球激活蛋白具有功能上的活性。更重要的是，大腸桿菌的表達系統能夠產生大量的重組嗜中性白血球激活蛋白以提供基礎研究、疫苗的開發、或是藥物的設計。

Helicobacter pylori is considered the most common infectious agent among humans worldwide. Recently, the neutrophil-activating protein (NAP), a H. pylori protein that is highly immunogenic in human, has been identified. However, purification of NAP from H. pylori is difficult due to its fastidious growth in microaerophilic condition and poor yield. To date, it has never been reported that the functional recombinant NAP were purified from E. coli expression system. To determine whether the functional dodecameric NAP could be obtained from E. coli expression system, both recombinant native and His-tag fusion NAPs expressed in E. coli were purified and characterized. By size exclusion and analytical ultracentrifuge analyses, both recombinant native and His-tag fusion NAPs are assembled into multimeric forms. By circular dichroism analysis, the secondary structures of both purified recombinant NAPs were identified as the typical a-helix. By luminol-enhanced chemiluminescent assay and westen blotting, both the recombinant native and His-tag fusion NAPs were able to cause the O2.- release from cells and increase phosphorylation of extracellular regulated kinase (ERK). From my E. coli expression system, a large amount of recombinant NAPs were obtained. Multimeric assembly and activity of both recombinant native and His-tag fusion NAPs are similar to those of native NAP from H. pylori. The results indicate that the recombinant NAPs obtained from our E. coli expression system is functionally active. Importantly, this E. coli expression system can provide a lot of recombinant NAPs for basic studies, vaccinal development, or drug design.

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