Transcriptional regulation of the Nε-fructoselysine metabolism in Escherichia coli by global and substrate-specific cues

Thermally processed food is an important part of the human diet. Heat-treatment, however, promotes the formation of so-called Amadori rearrangement products, such as fructoselysine. The gut microbiota includingEscherichia colican utilize these compounds as a nutrient source. While the degradation route for fructoselysine is well described, regulation of the corresponding pathway genesfrlABCDremained poorly understood. Here, we used bioinformatics combined with molecular and biochemical analyses and show that fructoselysine metabolism inE. coliis tightly controlled at the transcriptional level. The global regulator CRP (CAP) as well as the alternative sigma factor sigma 32 (RpoH) contribute to promoter activation at high cAMP-levels and inside warm-blooded hosts, respectively. In addition, we identified and characterized a transcriptional regulator FrlR, encoded adjacent tofrlABCD, as fructoselysine-6-phosphate specific repressor. Our study provides profound evidence that the interplay of global and substrate-specific regulation is a perfect adaptation strategy to efficiently utilize unusual substrates within the human gut environment.

Automated summary

Thermally processed foods contain compounds such as fructoselysine, which can be utilized by gut microbiota as a nutrient source. The metabolism of fructoselysine in E. coli is tightly controlled at the transcriptional level, with the global regulator CRP (CAP) and the alternative sigma factor sigma 32 (RpoH) playing key roles in promoter activation. Additionally, a transcriptional regulator FrlR has been identified as a specific repressor for fructoselysine-6-phosphate, highlighting the complex interplay between global and substrate-specific regulation for efficient utilization of unusual substrates in the human gut environment.