Aberrant Cell Division and Random FtsZ Ring Positioning in Escherichia coli cpxA * Mutants

Abstract

In Escherichia coli, certain mutations in thecpxA gene (encoding a sensor kinase of a two-component signal transduction system) randomize the location of FtsZ ring assembly and dramatically affect cell division. However, deletion of the cpxRA operon, encoding the sensor kinase and its cognate regulator CpxR, has no effect on division site biogenesis. It appears that certain mutant sensor kinases (CpxA*) either exhibit hyperactivity on CpxR or extend their signalling activity to one or more noncognate response regulators involved in cell division.

Activation of the Cpx regulon destabilizes the F plasmid transfer activator, TraJ, via the HslVU protease in Escherichia coli

“…Substrates of HslVU include the cell division inhibitor SulA (Wu et al, 1999), and the capsule synthesis regulatory protein RcsA (Kuo et al, 2004), with both proteins being coregulated by the Lon protease. Aberrant cell division and randomized FtsZ ring assembly have been observed in cpxA* cells by Pogliano et al (1998) possibly as a result of the rapid degradation of SulA, a substrate of HslVU, which is activated by the Cpx system. Interestingly, the filamentous phenotype of cpxA101* cells is suppressed by the hslV mutation in IL1 (cpxA101* hslV) as revealed by electron microscopy (I.C.…”

The CpxRA Signal Transduction System of Escherichia coli : Growth-Related Autoactivation and Control of Unanticipated Target Operons

“…The transductants were selected at 37°C for tetracycline resistance (20 g/ml) and scored for arginine (0.6 mM) auxotrophy on glucose minimal medium, resulting in the isolation of strain ECL3500. ⌬(cpxRA) 2 was then P1 transduced from strain ECL1212 (29) into strain ECL3500. The transductants were selected for growth on glucose minimal medium free of arginine and scored for sensitivity to tetracycline and CuCl 2 (4 mM) (cpx deletion phenotype) (8a), resulting in the isolation of strain ECL3501.…”

“…Certain mutant versions of the CpxA sensor kinase (CpxA*) cause a variety of seemingly unrelated phenotypes. These include a decreased ability to perform conjugation (16,35,36); diminished assembly of lipoprotein and OmpF in the cell envelope (19,20); random septum positioning during cell division (29); lost ability to grow on succinate (31), L-lactose (3,28), and L-proline (27); acquired ability to grow on L-serine (24,25,38); partial isoleucine and valine auxotrophy (18,39); increased sensitivity to high temperature (16), sodium dodecyl sulfate (3), and hydrogen peroxide (8a); enhanced tolerance to high pH (5) colicins A and K (26); increased resistance to the aminoglycoside antibiotics amikacin and kanamycin (31,40); and decreased sensitivity to CuCl 2 (8a, 43). CpxA* proteins were shown to retain their kinase activity but to lack the ability to dephosphorylate CpxR-P, the phosphorylated form of the cognate response regulator (32).…”

The Yersinia pseudotuberculosis Cpx envelope stress system contributes to transcriptional activation of rovM

“…In the absence of ECSs, CpxA phosphatase activity dominates over its kinase activity to limit levels of CpxR~P through a feedback inhibitory mechanism [28] that acts in concert with the inhibitory function of the periplasmic regulatory protein, CpxP [14,29,30]. This means that bacterial strains deficient in CpxA phosphatase activity, or a cpxA deletion mutant lacking both phosphatase and kinase activities, are prone to accumulated active phosphorylated CpxR [28,[31][32][33][34][35]. Initially, it was not intuitively obvious how CpxR is phosphorylated without CpxA, but now it is clear that this can occur through the indiscriminate action of low molecular weight high-energy phosphodonors such as Acetyl phosphate, which are typically by-products of metabolism [28,[36][37][38][39][40].…”

“…DNase I foot-printing assays were performed to investigate the binding of CpxR~P to a region within these DNA fragments of the rovM promoter. The32 P labelled FP-D (B) and FP-B (C) sense strands of parent and mutated DNA fragments were incubated with CpxR~P at the following final concentrations: 0 nM, lane a and b (indicated by "-"); 100 nM, lane c; 200 nM, lane d; 400 nM, lane e; 600 nM, lane f, 800 nM, lane g. Reactions were resolved by denaturing PAGE and analysed with a Molecular Dynamics PhosphorImager. Labelled pBR322 DNA digested with MspI (New England Biolabs) was used as a size marker (lane a).…”