大肠杆菌trxA缺陷菌株NTCC™ (E. coli trxA knockout strain) BioVector NTCC典型培养物保藏中心

大肠杆菌trxA缺陷菌株 (E. coli trxA knockout strain) 是指大肠杆菌中 trxA 基因被敲除或失活的菌株。

trxA 基因和硫氧还蛋白 (Thioredoxin A, TrxA) 的作用

trxA 是一个编码硫氧还蛋白 (Thioredoxin A, TrxA) 的基因。硫氧还蛋白是一种广泛存在于生物体内的蛋白质，它在大肠杆菌的生理活动中扮演着多个关键角色：

• 氧化还原反应: TrxA 是一种小分子氧化还原蛋白，其核心功能是通过其活性中心的二硫键与二巯基之间的可逆氧化还原反应，参与细胞内的多种氧化还原过程。

• 蛋白质折叠与二硫键还原: 在大肠杆菌的细胞质中，TrxA 主要负责还原蛋白质中的二硫键。这对于蛋白质的正确折叠和维持其活性至关重要。

• 作为分子伴侣: 尽管 TrxA 本身不属于典型的分子伴侣蛋白，但它具有类似的功能，可以促进外源蛋白的可溶性表达，减少包涵体的形成。

• DNA 复制: TrxA 也是噬菌体 T7 DNA 聚合酶的一个重要亚基，是其过程持续性因子。

trxA 缺陷菌株的特性和应用

由于 trxA 基因对于大肠杆菌的正常生长和生理活动至关重要，trxA 缺陷菌株通常会表现出以下一些特点：

• 生长受限: 缺乏 trxA 基因会影响大肠杆菌的正常生长，因为细胞内许多重要的氧化还原反应和蛋白质折叠过程会受到阻碍。

• 细胞质氧化环境: 正常情况下，大肠杆菌的细胞质是一个还原性环境。当 trxA 基因缺失后，细胞质的还原能力会大大降低，环境变得更具氧化性。

• 研究工具: trxA 缺陷菌株通常被用于以下研究：

  • 蛋白质表达: 在基因工程中，有时会使用 trxA 缺陷菌株，并结合其他基因改造，来构建一个有利于二硫键形成的氧化性细胞质环境，从而高效表达那些需要二硫键才能正确折叠的重组蛋白。

  • 基因互补实验: 研究人员可以使用这种缺陷菌株来测试其他基因（如来自不同生物的硫氧还蛋白基因）是否能够“互补”或恢复其正常功能。

  • 研究氧化还原平衡: 它是研究细胞内氧化还原平衡和硫氧还蛋白系统功能的重要工具。

  
  

An E. coli trxA knockout strain is a strain of the bacterium Escherichia coli where the trxA gene has been deleted or inactivated.

The Role of the trxA Gene and Thioredoxin A (TrxA)

The trxA gene encodes for thioredoxin A (TrxA), a small protein that plays a crucial role in the physiology of E. coli and many other organisms. Its key functions include:

• Redox Reactions: TrxA is a redox-active protein that participates in numerous intracellular redox processes through the reversible oxidation and reduction of its active-site disulfide bond.

• Protein Folding: It is primarily responsible for reducing disulfide bonds within proteins in the E. coli cytoplasm. This is essential for the proper folding of many proteins and for maintaining their biological activity.

• Molecular Chaperone Activity: Although not a classic chaperone, TrxA can promote the soluble expression of foreign proteins, which helps to prevent the formation of inclusion bodies (insoluble protein aggregates).

• DNA Replication: TrxA is a crucial subunit of the bacteriophage T7 DNA polymerase, acting as its processivity factor to ensure efficient DNA synthesis.

Characteristics and Applications of a trxA Knockout Strain

Because the trxA gene is vital for normal growth and physiological functions, a trxA knockout strain typically has several distinct characteristics:

• Growth Defects: The absence of the trxA gene impairs normal bacterial growth, as many essential redox reactions and protein folding processes are hindered.

• Oxidizing Cytoplasm: The E. coli cytoplasm is normally a reducing environment. When the trxA gene is deleted, the reducing capacity of the cytoplasm is significantly reduced, making the environment more oxidizing.

• Research Tool: These strains are commonly used in research for several purposes:

  • Protein Expression: In genetic engineering, trxA knockout strains can be used to create a more oxidizing cytoplasmic environment. This can be beneficial for the high-yield expression of recombinant proteins that require the formation of disulfide bonds to fold correctly.

  • Complementation Studies: Researchers can use this knockout strain to test whether other genes (e.g., thioredoxin genes from different organisms) can "complement" or restore the normal function of the cell.

  • Studying Redox Balance: It serves as a valuable tool for investigating cellular redox balance and the functions of the thioredoxin system.

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