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標題: 利用X-ray繞射技術研究植物病原菌Xanthomonas campestris的XC2113,XC2712及XC5630蛋白
The studies of XC2113, XC2712 and XC5630 proteins from a plant pathogen Xanthomonas campestris by X-ray diffraction technique
作者: 邱國城
Chiu, Kuo-Cheng
關鍵字: X-ray 繞射技術;X-ray diffraction technique;Xanthomonas campestris;glycine cleavage system;YaeQ;ketosteroid isomerase
出版社: 生物化學研究所
Xanthomonas campestris pv. campestris為格蘭氏陰性菌,主要感染十字花科植物,造成農業損失,因此研究這株菌的蛋白功能將有助於減少農業上的損失。其中XC2113利用BLAST 預測為YaeQ 蛋白。而在其它菌株中,例如在Salmonella enterica sv. Typhimurium 菌株中,YaeQ 蛋白調控hemolysin 致病毒素的表現。而hemolysin 主要的功能是分解紅血球,造成溶血的作用。XC2113在XCC的作用機制並不清楚,但可能會調控Xcc 其它的致病毒素,進而感染十字花科植物,造成植物腐壞。目前已經成功得到XC2113的可溶性蛋白,並且找到合適的結晶條件。經過X-ray 繞射技術分析後,其解析度達到1.28Å。未來將利用結構分析,了解該蛋白的功能。另外還分別得到XC2712及XC5630的蛋白結晶。而利用序列比對的方法,XC2712被預測具有glycine cleavage system (GCS) transcriptional repressor的功能。不論在原核生物或是真核生物中,GCS 都是很重要的調節機制,藉由此系統可以將甘胺酸分解成NH3、CO2和一個單一碳單元。目前XC2712雖可得到很多不同晶形的晶體,但由於結晶速度太快,以致於得到的晶體都太小。X-ray 繞射技術分析後,也無法得到很好的解析度。未來嘗試以晶種結晶的方式,試圖得到較大的晶體。利用BLAST 作分析,判斷XC5630 的功能可能為酮固醇異構酶(ketosteroid isomerase)。酮固醇異構酶可以改變類固醇環上雙鍵的位置。這種酮固醇調控養份分解,產生生物體所需的能量。然而此調控機制還不清楚,因此研究XC5630將有助於了解生命體如何產生這種類固醇,進而了解整個能量代謝的機制。XC5630得到一個晶形不錯的結晶,晶體大小為0.3×0.2×0.1 mm 。但以X-ray 繞射技術分析後,卻沒有辨法得到很好的解析度。

Xanthomonas campestris pv. campestris (Xcc) is a gram-negative bacterium. It is phytopathogenic to cruciferous plants and causes worldwide agricultural loss. To reduce this loss, it is necessary to find Xcc pathogenic factors and to block their functions. Among them, XC2113 was predicted to belong to the YaeQ family by a BLAST search, and proposed to regulate the expression of toxins such as hemolysin in other bacterial strains. For example, the YaeQ in S. enterica sv. Typhimurium play the function of hemolysin. The chief function of hemolysin is presumably to decompose red blood cell. Although the function of XC2113 in Xcc is not clear yet, it may infect cruciferous plants, causing rot disease through the release of hemolysin. The XC2113 protein has been successfully expressed and purified, and crystals suitable for X-ray diffraction (reached to 1.28 ) have been obtained. By analyzing its tertiary structure, it may be possible to decipher its function. Besides XC2113, the XC2712 and XC5630 proteins were also successfully crystallized. XC2712 is predicted as a glycine cleavage system (GCS) transcriptional repressor by sequence alignment. GCS is a very important mechanism in every organism to decompose glycine into NH3, CO2 and C1 unit, which is an important source of methyl donor in many biosynthesis reactions. At present, many different kinds of small crystals were observed for XC2712. But no good data could be collected yet, possibly due to the fast crystallization. Seeding method can be tried to improve the crystal size. XC5630 is predicted as a ketosteroid isomerase by a BLAST serch, which can change the position of double bond of ketosteroids. This ketosteroid can control the decomposition of nutrient to energy. Good-liking crystals of XC5630 of mm size have been obtained. However, no good data could be derived from this crystal, possibly due to their high mosacity values.
Appears in Collections:生物化學研究所

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