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bioRxiv · 10.1101/639088

A Novel L-Serine Exporter and Its Positive Regulator in Corynebacterium glutamicum

Zhang, X.·Gao, Y.·Chen, Z.·Xu, G.·Li, H.·Shi, J.-S.·Koffas, M. A.·Xu, Z.
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Abstract

Exporters play an essential role in the fermentative production of amino acids. In Corynebacterium glutamicum, ThrE, which can export O_SCPCAPLC_SCPCAP-threonine and O_SCPCAPLC_SCPCAP-serine, is the only identified O_SCPCAPLC_SCPCAP-serine exporter so far. In this study, a novel O_SCPCAPLC_SCPCAP-serine exporter NCgl0580 was identified and characterized in C. glutamicum {Delta}SSAAI (SSAAI), and named as SerE (encoded by serE). Deletion of serE in SSAAI led to a 56.5% decrease in O_SCPCAPLC_SCPCAP-serine titer, whereas overexpression of serE compensated for the lack of serE with respect to O_SCPCAPLC_SCPCAP-serine titer. A fusion protein with SerE and enhanced green fluorescent protein (EGFP) was constructed to confirm that SerE localized at the plasma membrane. The function of SerE was studied by peptide feeding approaches, and the results showed that SerE is a novel exporter for O_SCPCAPLC_SCPCAP-serine and O_SCPCAPLC_SCPCAP-threonine in C. glutamicum. Subsequently, the interaction of a known O_SCPCAPLC_SCPCAP-serine exporter ThrE and SerE was studied, and the results suggested that SerE is more important than ThrE in O_SCPCAPLC_SCPCAP-serine export in SSAAI. Probe plasmid and electrophoretic mobility shift assays (EMSA) revealed NCgl0581 as the transcriptional regulator of SerE. Comparative transcriptomics between SSAAI and the NCgl0581 deletion strain showed that NCgl0581 regulated the transcription of 115 genes in C. glutamicum, among which the transcriptional level of NCgl0580 decreased 280-fold in a NCgl0581 deletion strain, indicating that NCgl0581 is a positive regulator of SerE. Thus, this study provides a novel target for O_SCPCAPLC_SCPCAP-serine and O_SCPCAPLC_SCPCAP-threonine export engineering as well as a novel global transcriptional regulator NCgl0581 in C. glutamicum.\n\nImportanceExporters are gaining increasing attention for improving industrial production of amino acids. This study identified a novel exporter NCgl0580 for O_SCPCAPLC_SCPCAP-serine and O_SCPCAPLC_SCPCAP-threonine in C. glutamicum, and its positive regulator (NCgl0581), which was shown to be a novel global transcriptional regulator in C. glutamicum. This study provides a new target for engineering efflux of O_SCPCAPLC_SCPCAP-serine and O_SCPCAPLC_SCPCAP-threonine, expands the exporter and transcriptional regulator family, and enriches our understanding of amino acid transport system in C. glutamicum.

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Zhang, X., Gao, Y., Chen, Z., Xu, G., Li, H., Shi, J.-S., Koffas, M. A., Xu, Z.. 2019-05-16. A Novel L-Serine Exporter and Its Positive Regulator in Corynebacterium glutamicum. https://doi.org/10.1101/639088

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