胃幽門螺旋桿菌是一種人類社會中普遍存在的病原菌，它能適應在酸性的環境中且能生存在人類的胃裡。HP0232，是胃幽門螺旋桿菌其中的一個基因，被The Institute for Genomic Research (TIGR) 預測該基因的產物是一可能參與鞭毛運動的分泌性蛋白質。以DNA microarray為研究方法的實驗中指出HP0232基因可在pH 5.5的洋菜培養基所培養的菌中被酸誘導而表現。此外，功能性基因的研究顯示HP0232也是幽門螺旋桿菌在胃中形成菌落時所需的基因。當本實驗室成功地建構並表現HP0232基因在大腸桿菌株時，而且拮抗HP0232蛋白質的多抗血清也被成功地製造之後，針對重組性HP0232蛋白質的功能性研究在本實驗中持續地進行。
利用HP0232蛋白質的多抗血清進行的西方點墨法測知，以pH 5.5的Brucella洋菜培養基培養48小時的菌，比起以pH 7.2所培養的菌，大約有多2倍的HP0232蛋白質的表現。這一個被酸誘導的現象能在72及96小時的酸處理中持續地表現。以agar slant及Brucella broth培養的細菌樣本中，pH 7.2與pH 5.5處理後，得到等量的HP0232蛋白質表現。但是HP0232蛋白質懸浮在24-48小時培養的細菌培養液的發現，顯示它是一個分泌性的蛋白質。
在50-800 µg/ml的HP0232蛋白質處理下，10 µl的菌液在pH 5.5的洋菜培養基中能形成比在pH 7.2的培養基中還要大的生長區域。而且400 µg/ml的HP0232蛋白質能使細菌的生長區域 (代表細菌的運動力) 到最大的極限。測量urease活性的結果 (細菌附著率實驗) 得知50 µg/ml的HP0232蛋白質能幫助幽門螺旋桿菌附著到AGS細胞上。然而，當AGS細胞以100 µg/ml的HP0232蛋白質處理之後，並無法造成細胞的凋亡。
為了得知在HP0232蛋白質少掉前面一段signal peptide之後的活性的變化，得自於大腸桿菌表現系統的N端截斷的HP0232蛋白質 (NT-HP0232) 也被用來進行各式的功能性實驗。理論上，由結構上較接近幽門螺旋桿菌所分泌出的NT-HP0232蛋白質所進行的研究，所得到的結果也較接近真實的情況。

Helicobacter pylori is a common pathogen in humans, which can adapt to acid environments and survive in the human stomach. HP0232, one of the H. pylori genes, was predicted as a secreted protein involved in flagellar motility by The Institute for Genomic Research (TIGR). DNA microarray-based study indicated that HP0232 gene can be acid-induced at pH 5.5 in the agar plate culture. Another functional genomic research showed that HP0232 gene is needed for gastric colonization. Since the cloning and expression of the HP0232 gene in E. coli was successful for anti-HP0232 antiserum production in our lab, continuous functional studies of recombinant HP0232 protein were carried out in this study.
After Western analysis in using anti-HP0232 rabbit serum, approximate 2-fold HP0232 protein expression was found from samples cultured for 48 h on Brucella agar plates at pH 5.5, compared to samples at pH 7.2. This acid-induced expression can be prolonged for 72 h and 96 h in acid exposure. Similar amounts of expressed HP0232 protein were found from suspension samples harvested from agar slant cultures or Brucella broth cultures at pH 7.2 and 5.5. HP0232 protein, presented in supernatant of 24-48 h bacteria culture, appeared as secreted protein.
In the presence of 50-800 µg/ml of HP0232 protein, 106 bacteria per 10 µl-spot on agar plates at pH 5.5 would form larger growth zone than those at pH 7.2. Further, 400 µg/ml of rec-HP0232 protein can enhance the bacteria growth zone (represented as the bacteria motility) to the maximum. The results from urease activity measurement (represented as the adhesion rate assay) showed that 50 µg/ml of HP0232 protein will increase the H. pylori adhesion to AGS cells. However, no extra sub-G1 apoptosis was found in AGS cells after 24-h culture containing 100 µg/ml of HP0232 protein.
To investigate the alteration of functional activity when the signal peptide of HP0232 protein was truncated, the N-truncated HP0232 protein (NT-HP0232), that was cloned, expressed, and purified by the E. coli expression system, was used in these functional analyses. Theoretically, it is more conformed to the real situation, if the functional studies were resolved by using the NT-HP0232 protein which is similar to that secreted by H. pylori.

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