十字花科黑腐病菌為革蘭氏陰性菌，能夠藉由Type II secretion pathway分泌胞外酵素而感染十字花科植物。Type II secretion pathway是革蘭氏陰性菌分泌胞外蛋白的主要機制之一，而這些胞外蛋白往往是使宿主致病的主要原因。故致力研究Type II secretion pathway的分子機制，期望能獲得抑制病源菌感染宿主的方法。
Type II secretion pathway的成員中的GpsG、H、I、J、K蛋白被認為會形成類似纖毛狀的結構，與推動胞外蛋白通過外膜有關。過去, 雖然以cross-linking的實驗發現在P. aeruginosa中GspG蛋白和GspH、I、J蛋白間存在著交互作用，然而對於其中詳細的交互作用機制目前仍無所知。所以本篇論文的目的即是針對十字花科黑腐病菌XpsG、H、J蛋白之間交互作用關係作詳細的探討。實驗中以膠層過濾層析法以及Ni-NTA 親合性管柱層析法分別分析XpsG、H、J的分子特性及彼此間的交互作用。結果發現：a. XpsH-his6蛋白與XpsG蛋白之間具有交互作用；b. XpsH-his6蛋白會與XpsJ蛋白產生交互作用並影響XpsJ蛋白在膠層過濾層析下的分佈；c. XpsH蛋白會幫助XpsG-XpsJ-his6複合體的形成。綜合以上結果可以知道：XpsH蛋白能夠幫助XpsJ與XpsG蛋白之間的結合並形成XpsG-XpsH-XpsJ的複合體。
Xanthomonas campestris pv. campestris exports a number of hydrolytic enzymes to infect plants using type II secretion pathway. Type II secretion pathway is the main terminal branch of the general secretion pathway in gram-negative bacteria for extracellular secretion of toxins and hydrolytic enzymes. Extracellular secretion of proteins is regarded as a major virulence mechanism in bacteria infection. In order to resolve the problem of bacteria infection, the study of type II secretion pathway is important.
The members of type II secretion pathway, XpsGHIJK, were assumed to form pilus-like structure and push secreted proteins through the outer membrane. In the past, the cross-linking experiment in P. aeruginosa revealed that GspG could interact with GspH,-I,-J, but the detail protein-protein interactions among GspG, -H, -I, -J is still unknown. In this study, analysis of the interactions between XpsG, -H, -J in Xanthomonas campestris pv. campestris by gel filtration and Ni-NTA affinity chromatography showed that : a. XpsH-his6 could interact with XpsG; b. XpsH-his6 could interact with XpsJ and change the fractionation of XpsJ in gel filtration chromatography ; c. XpsH could assist the formation of XpsG-XpsJ-his6 complex. These observations suggest that XpsH could regulate the complex formation of XpsG-XpsH-XpsJ.
