A Novel Regulatory Cascade Involving BluR, YcgZ, and Lon Controls the Expression of Escherichia coli OmpF Porin

Abstract

In Escherichia coli, OmpF is an important outer membrane protein, which serves as a passive diffusion pore for small compounds including nutrients, antibiotics, and toxic compounds. OmpF expression responds to environmental changes such as temperature, osmolarity, nutrients availability, and toxic compounds via complex regulatory pathways involving transcriptional and post-transcriptional regulation. Our study identified a new regulatory cascade that controls the expression of OmpF porin. This pathway involves BluR, a transcriptional regulator repressing the expression of the ycgZ-ymgABC operon. We showed that BluR was responsible for the temperaturedependent regulation of the ycgZ-ymgABC operon. Furthermore, our results showed that independent expression of YcgZ led to a decreased activity of the ompF promoter, while YmgA, YmgB, and YmgC expression had no effect. We also determined that YcgZ accumulates in the absence of the Lon protease. Thus, mutation in bluR leads to derepression of ycgZ-ymgABC transcription. With a second mutation in lon, YcgZ protein accumulates to reach levels that do not allow increased expression of OmpF under growth conditions that usually would, i.e., low temperature. With BluR responding to blue-light and temperature, this study sheds a new light on novel signals able to regulate OmpF porin.

The Escherichia coli MarA protein regulates the ycgZ‐ymgABC operon to inhibit biofilm formation

“…). We also note that Duval and coworkers reported the accumulation of ycgZ ‐ ymgABC ‐encoded proteins in strains lacking the Lon protease (Duval et al , ). This is due to Lon targeting MarA for degradation and levels of MarA thus increasing substantially in Lon deficient cells (Martin et al , ).…”

Valine-Induced Isoleucine Starvation in Escherichia coli K-12 Studied by Spike-In Normalized RNA Sequencing

“…Besides these, the data set also contains many smaller gene categories that will be of interest to specific research sub fields. For example, mRNA of the conserved BluR-repressed operon ycgZ-ymgABC, which were completely repressed during steady-state growth, were among the genes most strongly up-regulated upon starvation ( Supplementary Table S8), suggesting an unidentified regulatory mechanism that is unrelated to the known BluR signals; blue light and low temperature, for the YcgZ regulator of OmpF porin expression and the Ymg biofilm modulators (Tschowri et al, 2012;Duval et al, 2017). Finally, at least four (alaE, gcvB, dadA, dadX) of the 20 genes that respond most strongly in our dataset are likely responding to the sudden addition of L-valine rather than the starvation for isoleucine ( Figure 10).…”

Proteomics Reveal the Effect of Exogenous Electrons on Electroactive Escherichia coli

“…Excluding uncharacterized proteins, the up-regulated outer membrane protein OmpF ( E.coli-MtrCBA/E.coli-control Ratio = 1.653) was further identified. OmpF is a highly abundant primary porin in E. coli , which enables passive diffusion of hydrophilic molecules and influences outer membrane permeability ( Duval et al, 2017 ).…”