Expression of the pfl Gene and Resulting Metabolite Flux Distribution in nuo and ackA-pta E. coli Mutant Strains

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• 作者：Randeep Singh ; Yea-Tyng Yang ; Biqing Lu ; George N. Bennett ; and Ka-Yiu San
• 刊名：Biotechnology Progress
• 出版年：2006
• 出版时间：June 2006
• 年：2006
• 卷：22
• 期：3
• 页码：898 - 902
• 全文大小：181K
• 年卷期：v.22,no.3(June 2006)
• ISSN：1520-6033

文摘

Our laboratory previously studied the interaction between nuo and the acetate-producing pathwayencoded by ackA-pta in Escherichia coli. We examined metabolic patterns, particularly the ethanoland acetate production rates, of several mutant strains grown under anaerobic growth conditions.Since the pyruvate formate-lyase (PFL) pathway is the major route for acetyl-CoA and formateproduction under anaerobic conditions, we examined the effects of nuo and ackA/pta mutationson the expression of pyruvate formate-lyase (pfl) under anaerobic conditions. The ackA-pta mutanthas a pfl::lacZ expression level much higher than that of the wild-type strain, and cultures alsoexhibit the highest ethanol production. Real-time PCR demonstrated that the adhE gene expressionin the ack-pta mutant strain was approximately 100 fold that of the same gene in the ackA-ptanuo mutant strain. This result correlates with the observed ethanol production rates in culturesof the strain. However, the lack of exact correlation between the ethanol production rates andthe RT-PCR data suggests additional regulation actions at the posttranslation level. In addition,the activity of the pfl gene as indicated by mRNA levels was also considerably greater in theack-pta mutant. We can conclude that deletions of nuo and ack/pta can partially affect theexpression of the genes encoding adhE and pfl under anaerobic conditions.