Biology subjects

Koffas, M. A.

Publications and source records attributed to Koffas, M. A..

3 recordsLinked to original sources

bioRxiv2026

Fine-tuned synthetic transcription factors for production of 3' phosphoadenosine-5'-phosphosulfate in yeast

Technologies developed over the past decade have made Saccharomyces cerevisiae a promising platform for producing various natural products. Balancing multi-enzyme expression, while maintaining robust microbial growth, remains a limiting factor for engineering long biosynthetic pathways in yeast. Here, we improved the transcriptional capacity of our previously developed isopropyl {beta}-D-1-thiogalactopyranoside (IPTG)-inducible synthetic transcription factors (synTFs) derived from the plant JUB1 DNA-binding domain. To this end, at cysteine positions within surface-exposed loop regions of a JUB1-derived DNA-binding scaffold, we introduced a short peptide to enhance loop flexibility while providing local stability and orientation. The generated synTFs, so-called JUB1-X synTFs, varying in strength, have been successfully used to improve the synthesis of 3-phosphoadenosine 5-phosphosulfate (PAPS), a universal sulfate donor necessary for the synthesis of bioactive molecules, including therapeutic glycosaminoglycans and sulfolipids. Using only this engineered yeast strain in simple batch culture, PAPS accumulation of 21.4 {+/-} 5.8 mg g-1 cdw was achieved after only 5 hours of inducing the expression of JUB1-X synTFs. Beyond PAPS production, the design principle demonstrated here provides a generalizable strategy to fine-tune other plant-derived synTFs, expanding the regulatory capabilities of existing synTF collections. Together, this work offers a modular, scalable approach to constructing high-performance gene circuits and supports the development of yeast cell factories for complex metabolic and synthetic biology applications.

synthetic biology↗

bioRxiv2020

A novel prokaryotic CRISPR-Cas12a based tool for programmable transcriptional activation and repression

Transcriptional perturbation using inactivated CRISPR-nucleases (dCas) is a common method in eukaryotic organisms. While rare examples of dCas9 based tools for prokaryotes have been described, multiplexing approaches are limited due to the used effector nuclease. For the first time, a dCas12a derived tool for the targeted activation and repression of genes was developed. Therefore, a previously described SoxS activator domain was linked to dCas12a to enable programmable activation of gene expression. Proof of principle of transcriptional regulation was demonstrated based on fluorescence reporter assays using the alternative host organism Paenibacillus polymyxa as well as Escherichia coli. Single target and multiplex CRISPR interference targeting the exopolysaccharide biosynthesis of P. polymyxa was shown to emulate polymer compositions of gene knock-outs. Simultaneous expression of 11 gRNAs targeting multiple lactate dehydrogenases and a butanediol dehydrogenase resulted in decreased lactate formation, as well as an increased butanediol production in microaerobic fermentation processes. Even though Cas12a is more restricted in terms of its genomic target sequences compared to Cas9, its ability to efficiently process its own guide RNAs in vivo makes it a promising tool to orchestrate sophisticated genetic reprogramming of bacterial cells or to screen for engineering targets in the genome. The developed tool will accelerate metabolic engineering efforts in the alternative host organism P. polymyxa and might be also applied for other bacterial cell factories.

synthetic biology↗

bioRxiv2019

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

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.

bioengineering↗