Publications

• The membrane-integrated transcriptional activator CadC of Escherichia coli senses lysine indirectly via the interaction with the lysine permease LysP.

  Tetsch L., Koller C., Haneburger I., Jung K.

  In an acidic (pH 5.8) and lysine-rich environment Escherichia coli induces expression of the cadBA operon which encodes CadA, catalysing the decarboxylation of lysine to cadaverine, and CadB, the lysine/cadaverine antiporter. cadBA expression is dependent on CadC, a membrane-integrated transcripti ... >> More

  In an acidic (pH 5.8) and lysine-rich environment Escherichia coli induces expression of the cadBA operon which encodes CadA, catalysing the decarboxylation of lysine to cadaverine, and CadB, the lysine/cadaverine antiporter. cadBA expression is dependent on CadC, a membrane-integrated transcriptional activator which belongs to the ToxR-like protein family and directly binds to the DNA in the cadBA promoter region. Here we describe that CadC senses the extracellular lysine not directly but indirectly requiring the interplay with the lysine permease LysP. Biochemical analyses of isolated CadC or the periplasmic domain of CadC (CadC188-512) revealed an unexpectedly low affinity for lysine, making it unlikely that CadC is a direct sensor for this substrate. Moreover, CadC hybrid proteins, in which the transmembrane domain or single amino acids were replaced, supported lysine-independent cadBA expression but retained a pH-dependent regulation. These CadC mutants were resistant to the effect of an overproduction of LysP, which represses cadBA expression in wild-type cells. Our results suggest a model according to which CadC is inactivated by an interaction with LysP at a low external lysine concentration. When lysine is abundantly available, the interaction between LysP and CadC is released, and CadC becomes susceptible to activation by low pH. << Less

  Mol. Microbiol. 67:570-583(2008) [PubMed] [EuropePMC]

• The lysP gene encodes the lysine-specific permease.

  Steffes C., Ellis J., Wu J., Rosen B.P.

  Escherichia coli transports lysine by two distinct systems, one of which is specific for lysine (LysP) and the other of which is inhibited by arginine ornithine. The activity of the lysine-specific system increases with growth in acidic medium, anaerobiosis, and high concentrations of lysine. It i ... >> More

  Escherichia coli transports lysine by two distinct systems, one of which is specific for lysine (LysP) and the other of which is inhibited by arginine ornithine. The activity of the lysine-specific system increases with growth in acidic medium, anaerobiosis, and high concentrations of lysine. It is inhibited by the lysine analog S-(beta-aminoethyl)-L-cysteine (thiosine). Thiosine-resistant (Tsr) mutants were isolated by using transpositional mutagenesis with TnphoA. A Tsr mutant expressing alkaline phosphatase activity in intact cells was found to lack lysine-specific transport. This lysP mutation was mapped to about 46.5 min on the E. coli chromosome. The lysP-phoA fusion was cloned and used as a probe to clone the wild-type lysP gene. The nucleotide sequence of the 2.7-kb BamHI fragment was determined. An open reading frame from nucleotides 522 to 1989 was observed. The translation product of this open reading frame is predicted to be a hydrophobic protein of 489 residues. The lysP gene product exhibits sequence similarity to a family of amino acid transport proteins found in both prokaryotes and eukaryotes, including the aromatic amino acid permease of E. coli (aroP) and the arginine permease of Saccharomyces cerevisiae (CAN1). Cells carrying a plasmid with the lysP gene exhibited a 10-to 20-fold increase in the rate of lysine uptake above wild-type levels. These results demonstrate that the lysP gene encodes the lysine-specific permease. << Less

  J. Bacteriol. 174:3242-3249(1992) [PubMed] [EuropePMC]

• New insights into the interplay between the lysine transporter LysP and the pH sensor CadC in Escherichia coli.

  Rauschmeier M., Schueppel V., Tetsch L., Jung K.

  The coordination of signal transduction and substrate transport represents a sophisticated way to integrate information on metabolite fluxes into transcriptional regulation. This widely distributed process involves protein-protein interactions between two integral membrane proteins. Here we report ... >> More

  The coordination of signal transduction and substrate transport represents a sophisticated way to integrate information on metabolite fluxes into transcriptional regulation. This widely distributed process involves protein-protein interactions between two integral membrane proteins. Here we report new insights into the molecular mechanism of the regulatory interplay between the lysine-specific permease LysP and the membrane-integrated pH sensor CadC, which together induce lysine-dependent adaptation of E. coli under acidic stress. In vivo analyses revealed that, in the absence of either stimulus, the two proteins form a stable association, which is modulated by lysine and low pH. In addition to its transmembrane helix, the periplasmic domain of CadC also participated in the interaction. Site-directed mutagenesis pinpointed Arg265 and Arg268 in CadC as well as Asp275 and Asp278 in LysP as potential periplasmic interaction sites. Moreover, a systematic analysis of 100 LysP variants with single-site replacements indicated that the lysine signal is transduced from co-sensor to sensor via lysine-dependent conformational changes (upon substrate binding and/or transport) of LysP. Our results suggest a scenario in which CadC is inhibited by LysP via intramembrane and periplasmic contacts under non-inducing conditions. Upon induction, lysine-dependent conformational changes in LysP transduce the lysine signal via a direct conformational coupling to CadC without resolving the interaction completely. Moreover, concomitant pH-dependent protonation of periplasmic amino acids in both proteins dissolves their electrostatic connections resulting in further destabilization of the CadC/LysP interaction. << Less

  J. Mol. Biol. 426:215-229(2014) [PubMed] [EuropePMC]