INB-Lunch-Seminar

Targeting Mip proteins for the development of new antibacterials

Vijayan Ramachandran

 

The infectivity and intracellular survival of pathogenic bacteria such as Chlamydia and Legionella is correlated with a major virulence factor termed macrophage-infectivity potentiator (Mip). Infections with Chlamydia species are responsible for a number of severe medical conditions potentially resulting in infertility, blindness and pneumonia, Legionella is the etiological agent of Legionnaires' disease. Mip has been shown to possess peptidyl-prolyl-cis/trans-isomerase (PPIase) activity, but in-vivo substrates are still unknown. Previously we have determined the crystal structure of Mip from Legionella pneumophila to a resolution of 2.4 Å[1]. More recently, the structures of Mip from L. pneumophila and E. coli in complex with the potent PPIase inhibitors rapamycin[2] and FK506[3], respectively have been published. Utilizing available structural information, we developed a pharmacophore model including crucial interactions between the inhibitor molecules and active-site residues of Mip as restraints. Using a subset of the SPECS database of commercially available compounds as a basis, we employed our pharmacophore model to rank ~55,000 compounds and docked the top 500 into the active site of Legionella Mip as well as into the active sites of homology models for C. trachomatis and C. pneumoniae Mip. Interestingly, 38 compounds were found to be common among the top 50 docking solution in all three species. As residues of the active site are well conserved in Mip from Legionella and Chlamydia, the binding mode of each individual compound was found to be very similar. Based on their chemical structure, the compounds fall into 8 classes. The major class features a central triazole ring and includes 27 out of 38 compounds. The remaining classes include 1-3 compounds each. The identified compounds will be tested for their ability to inhibit the PPIase activity of Mip proteins in vitro and for antibacterial efficacy in vivo. Furthermore, we aim to determine the three-dimensional structure of corresponding complexes using X-ray crystallography.

 

1. Riboldi-Tunnicliffe, A., König, B., Jessen, S., Weiss, M.S-, Rahfeld, J., Hacker, J., Fischer, G. and Hilgenfeld, R.: Crystal structure of Mip, a prolylisomerase from Legionella pneumophila.

Nature Struct. Biol. 8:779-783, 2001.

2. Ceymann, A., Horstmann, M., Ehses, P., Schweimer, K., Paschke, A.K., Steinert, M. & Faber, C.: Solution structure of the Legionella pneumophila Mip-rapamycin complex. BMC Struct. Biol. 8:17, 2008.

3. Saul, F.A., Arié, J.P., Vulliez-le, N. B., Kahn, R., Betton, J.M. & Bentley, G, A.: Structural and functional studies of FkpA from Escherichia coli, a cis/trans peptidyl-prolyl isomerase with chaperone activity. J Mol Biol. 335: 595-608, 2004.

 

Zeit:	Freitag, den 28.05.2010, 12 Uhr c.t.
Ort:	Institut für Neuro- und Bioinformatik Seminarraum (1. OG, Raum 17) Ratzeburger Allee 160 (Geb. 64)