Polyamines are important for regulating biofilms and the exopolysaccharide of the biofilm matrix of Bacillus subtilis. Understanding how enzymes can regulate polyamine concentrations is critical for learning more about how these processes occur in diverse bacteria. Here, we describe the structure and function of another member of the spermidine/spermine acetyltransferases (SSAT) found in Bacilli. The SpeG enzyme from B. thuringiensis (BtSpeG) binds polyamines in its allosteric site and adopts a dodecameric oligomeric state similar to other SpeG enzymes from Gram-negative bacteria. Our kinetic results show the catalytic efficiency of BtSpeG was greater than any previously characterized SpeG to date, and in contrast to other SpeG proteins it exhibited very similar kinetic properties toward both spermine and spermidine. Similar to the SpeG enzyme from E. coli, BtSpeG was able to acetylate spermidine on the N1 and N8 positions. The turnover of BtSpeG toward spermine and spermidine was also two to three orders of magnitude greater than any other Bacilli SSAT enzyme that has been previously characterized. SpeG proteins from Bacilli, including B. cereus, B. thuringiensis and B. anthracis share nearly identical sequences and therefore our results likely provide insight into the structure/function relationship across multiple Bacillus species.

中文翻译：

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来自苏云金芽孢杆菌的SpeG多胺乙酰基转移酶形成十二聚体结构并表现出高催化效率。

多胺对于调节枯草芽孢杆菌的生物膜和生物膜基质的胞外多糖很重要。了解酶如何调节多胺浓度对于进一步了解这些过程如何在多种细菌中发生至关重要。在这里，我们描述了在杆菌中发现的另一个亚精胺/精胺乙酰转移酶（SSAT）成员的结构和功能。苏云金芽胞杆菌的SpeG酶（BtSpeG）在其变构位点结合多胺，并与来自革兰氏阴性菌的其他SpeG酶类似，采用十二聚体低聚状态。我们的动力学结果表明，BtSpeG的催化效率比迄今为止任何以前表征的SpeG都要高，并且与其他SpeG蛋白质相比，它对精胺和亚精胺都表现出非常相似的动力学特性。与来自大肠杆菌的SpeG酶类似，BtSpeG能够在N1和N8位置乙酰化亚精胺。BtSpeG转化为精胺和亚精胺的周转率也比以前鉴定的任何其他Bacilli SSAT酶都要大2至3个数量级。来自芽孢杆菌，苏云金芽孢杆菌和炭疽芽孢杆菌的芽孢杆菌的SpeG蛋白共享几乎相同的序列，因此我们的结果可能为深入了解多种芽孢杆菌物种的结构/功能关系提供了线索。