转谷氨酰胺酶基因启动子中的一个点突变体显著提高了来自茂源链霉菌TX1的微生物转谷氨酰胺酶的产量
Title：A point mutant in the promoter of transglutaminase gene dramatically
increased yield of microbial transglutaminase from Streptomyces mobaraensis TX1
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Abstract：Microbial transglutaminase (TGase) is widely used in food processing because of its ability to catalyze protein cross-linking. In this study, ultraviolet (UV) mutagenesis was used to create a mutant of Streptomyces mobaraensis TX1 with a high TGase yield, with a maximum yield of 37.51 ± 0.46 U/mL after 32 h of flask fermentation, and a 2.15-fold increase compared to the wild-type (WT) strain. The transcriptional level of the transglutaminase gene increased 50-fold in the mutant strain compared to the WT strain, and a point mutation was found in the promoter of transglutaminase gene. The evaluation results of the promoter function revealed that the high yield of microbial transglutaminase was primarily caused by the point mutation. Our results provided a significant information on the high-yield mechanism of microbial transglutaminase biosynthesis.
Results：
Conclusions：
In this study, UV mutagenesis yielded a high-yield mutant strain Sm2−1, which reached 37.51 ± 0.46 U/mL after 32 h of fermentation,with increased TGase production by 215 % compared to the WT strain,and was the highest increase in TGase yield among the reported mutant strains. The relative expression of the TGase gene in the high-yield mutant Sm2−1 improved significantly, which partly explained the high TGase yield capacity of the mutant. Sequenced analysis of the TGase gene was performed on the high-yield mutant Sm2−1 and the WT strain TX1, and the result showed that the gene sequence remained unchanged. Further analysis of the non-coding regions revealed a mu tation located at 417 bp upstream of the translation start site of TGase gene, located at the -10 Box of the TGase promoter. The evaluation of TGase promoters revealed that the expression of GFP improved clearly under the control of the mutated TGase promoter, indicating that the mutation in TGase promoter leads to an increase in transcriptional level of TGase gene, which leads to an improvement in TGase yield. Currently, little effort has been made to significantly increase the TGase yield result by a point mutation, and our research would provide valuable information for further research on the high-yield mechanism of TGase.
Contact: Li Zeran
E-mail:2778786229@qq.com