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A study on L-threonine and L-serine uptake in Escherichia coli K-12.

ABSTRACT: In the current study, we report the identification and characterization of the yifK gene product as a novel amino acid carrier in E. coli K-12 cells. Both phenotypic and biochemical analyses showed that YifK acts as a permease specific to L-threonine and, to a lesser extent, L-serine. An assay of the effect of uncouplers and composition of the reaction medium on the transport activity indicates that YifK utilizes a proton motive force to energize substrate uptake. To identify the remaining threonine carriers, we screened a genomic library prepared from the yifK-mutant strain and found that brnQ acts as a multicopy suppressor of the threonine transport defect caused by yifK disruption. Our results indicate that BrnQ is directly involved in threonine uptake as a low-affinity but high-flux transporter, which forms the main entry point when the threonine concentration in the external environment reaches a toxic level. By abolishing YifK and BrnQ activity, we unmasked and quantified the threonine transport activity of the LIV-I branched chain amino acid transport system and demonstrated that LIV-I contributes significantly to total threonine uptake. However, this contribution is likely smaller than that of YifK. We also observed the serine transport activity of LIV-I, which was much lower compared with that of the dedicated SdaC carrier, indicating that LIV-I plays a minor role in the serine uptake. Overall, these findings allow us to propose a comprehensive model of the threonine/serine uptake subsystem in E. coli cells.

SUBMITTER: Khozov AA

PROVIDER: S-EPMC10070963 | biostudies-literature | 2023

REPOSITORIES: biostudies-literature

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A study on L-threonine and L-serine uptake in Escherichia coli K-12.

Khozov Andrey A AA Bubnov Dmitrii M DM Plisov Eugeny D ED Vybornaya Tatiana V TV Yuzbashev Tigran V TV Agrimi Gennaro G Messina Eugenia E Stepanova Agnessa A AA Kudina Maxim D MD Alekseeva Natalia V NV Netrusov Alexander I AI Sineoky Sergey P SP

Frontiers in microbiology 20230321

In the current study, we report the identification and characterization of the yifK gene product as a novel amino acid carrier in E. coli K-12 cells. Both phenotypic and biochemical analyses showed that YifK acts as a permease specific to L-threonine and, to a lesser extent, L-serine. An assay of the effect of uncouplers and composition of the reaction medium on the transport activity indicates that YifK utilizes a proton motive force to energize substrate uptake. To identify the r ...[more]

PMID: 37025642

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Project description:BACKGROUND:Microbial de novo production of L-serine, which is widely used in a range of cosmetic and pharmaceutical products, has attracted increasing attention due to its environmentally friendly characteristics. Previous pioneering work mainly focused on L-serine anabolism; however, in this study, it was found that L-serine could be reimported through the L-serine uptake system, thus hampering L-serine production. RESULT:To address this challenge, engineering via deletion of four genes, namely, sdaC, cycA, sstT and tdcC, which have been reported to be involved in L-serine uptake in Escherichia coli, was first carried out in the L-serine producer E. coli ES. Additionally, the effects of these genes on L-serine uptake activity and L-serine production were investigated. The data revealed an abnormal phenomenon regarding serine uptake activity. The serine uptake activity of the ΔsdaC mutant was 0.798 nmol min-1 (mg dry weight) -1 after 30 min, decreasing by 23.34% compared to that of the control strain. However, the serine uptake activity of the single sstT, cycA and tdcC mutants increased by 34.29%, 78.29% and 48.03%, respectively, compared to that of the control strain. This finding may be the result of the increased level of sdaC expression in these mutants. In addition, multigene-deletion strains were constructed based on an sdaC knockout mutant. The ΔsdaCΔsstTΔtdcC mutant strain exhibited 0.253 nmol min-1 (mg dry weight) -1L-serine uptake activity and the highest production titer of 445 mg/L in shake flask fermentation, which was more than three-fold the 129 mg/L production observed for the parent. Furthermore, the ΔsdaCΔsstTΔtdcC mutant accumulated 34.8 g/L L-serine with a yield of 32% from glucose in a 5-L fermenter after 36 h. CONCLUSION:The results indicated that reuptake of L-serine impairs its production and that an engineered cell with reduced uptake can address this problem and improve the production of L-serine in E. coli.

Dataset Information

A study on L-threonine and L-serine uptake in Escherichia coli K-12.

Publications

A study on L-threonine and L-serine uptake in <i>Escherichia coli</i> K-12.

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