Structural and mutational analyses of Aes, an inhibitor of MalT in Escherichia coli.

The acyl esterase Aes effectively inhibits the transcriptional activity of MalT-the central activator of maltose and maltodextrin utilizing genes in Escherichia coli. To provide better insight into the nature of the interaction between Aes and MalT, we determined two different crystal structures of Aes-in its native form and covalently modified by a phenylmethylsulfonyl moiety at its active site serine. Both structures show distinct space groups and were refined to a resolution of 1.

Crystallization and preliminary X-ray analysis of Mlc from Escherichia coli.

Mlc is a prokaryotic transcriptional repressor controlling the expression of a number of genes encoding enzymes of the Escherichia coli phosphotransferase system (PTS), ptsG and manXYZ, the specific enzyme II for glucose and mannose PTS transporters, as well as malT, the gene of the global activator of the mal regulon. The mlc gene has been cloned into a pQE vector and recombinant protein with the point mutation R52H was expressed and purified as the selenomethionine-labelled derivative. Crystallization of SeMet-Mlc R52H was carried out using the vapour-diffusion method.

The crystal structure of Mlc, a global regulator of sugar metabolism in Escherichia coli.

Mlc from Escherichia coli is a transcriptional repressor controlling the expression of a number of genes encoding enzymes of the phosphotransferase system (PTS), including ptsG and manXYZ, the specific enzyme II for glucose and mannose PTS transporters. In addition, Mlc controls the transcription of malT, the gene of the global activator of the mal regulon. The inactivation of Mlc as a repressor is mediated by binding to an actively transporting PtsG (EIICB(Glc)).

Crystallization and preliminary X-ray analysis of a C-terminal TonB fragment from Escherichia coli.

The TonB protein located in the cell wall of Gram-negative bacteria mediates the proton motive force from the cytoplasmic membrane to specific outer membrane transporters. A C-terminal fragment of TonB from Escherichia coli consisting of amino-acid residues 147-239 (TonB-92) has been purified and crystallized. Crystals grew in space group P2(1) to dimensions of about 1.

Crystallization and preliminary X-ray analysis of Aes, an acetyl-esterase from Escherichia coli.

Aes belongs to the family of hormone-sensitive lipases and has acetyl-esterase activity. It is also known to control maltose uptake through interaction with MalT, the central regulator of the Escherichia coli maltose system. Aes was crystallized as an N-terminally His(6)-tagged protein both in the native form and with selenomethionine substitution.