Fundamental studies on development of chemotherapeutics targeting cell surface proteins which are essential for growth in Escherichia coli

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Fruitful results described in (1)〜(8) were obtained during the period of this research.(1) The crystal structures of LolA and Lo1B which are involved in the localization of lipoproteins, a major component of the outer membrane, were determined.(2) We showed that the Lol avoidance signal requires a critical length of negative charge at the second residue, and that phosphatidylethanolamine is important for the Lol avoidance function.(3) Five Trp residues which are conserved among Lo1B homologs in Gram-negative bacteria were shown to be important for the receptor activity.(4) We verified the mechanism underlying lipoprotein transfer from LolA to Lo1B is unidirectional and very efficient, but requires no energy input.(5) The random mutagenesis of 14 residues on LolA revealed crucial roles of the hydrophobic cavity and lid in the binding of lipoproteins and their transfer.(6) On the basis of the result that some LolD mutations lowered the ATPase activity of Lo1CDE without affecting that of LolD, the LolD motif was found to be critical for functional interplay with Lo1C / LolE.(7) Using a new screening method which was developed to identify new antibacterial agents targeting the Lol system, we screened for 2 compounds which inhibit the LolA function.(8) We found that a periplasmic protein, YbiS, is a major transpeptidase involved in the covalent linkage between the Lpp and peptidoglycan, using in vitro assay system. The results described above contribute to development of chemotherapeutics targeting cell surface proteins which are essential for growth in Escherichia coli