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Dr. Harald Engelhardt
Phone: +49 - 89 - 8578 2650
Structure of the Microbial Cell: Outer Membrane of Mycobacteria
Mycobacteria and Corynebacteria are members of the Gram-positive
Actinomycetales. These bacteria – and amongst them
Mycobacterium tuberculosis and relatives – are known for their exceptionally effective cell wall barrier and their high content of mycolic acids that are covalently linked to the peptidoglycan via an arabinogalactan polymer. Cryo-electron tomography and cryosections of vitirified cells disclosed the native organisation of cell wall lipids as a mycobacterial outer membrane. We are investigating its structure and the outer membrane proteins.
Bacterial Outer Membrane Proteins: Porins
The outer membrane of Gram-negative bacteria – as well as of mycobacteria – contains pore proteins that are weakly or strongy selective or even specific for molecules passing the membrane barrier. The porins represent the first gate for ions, nutrients, and drugs to enter the cell and they mediate the uptake via diffusion or translocation. The porin Omp32 from the bacterium
Delftia (Comamonas) acidovorans has a remarkably narrow pore, is highly anion-selective, and is particularly suited to study the molecular mechanisms of ion and nutrient translocation in the channel.
Microbial Surface Proteins: S-layers
S-layers are regularly arrayed surface proteins or glycoproteins, covering the entire cell from many species of
Archaea and Bacteria. S-layers typically interact with either the plasmic membrane (archaea), the peptidoglycan (Gram-positive bacteria) or the outer membrane (Gram-negative bacteria). The determination of S-layer structures is still a domain of electron microscopy and cryo-electron tomography. Our laboratory studied the 3D structure of many archaeal and bacterial S-layers. Now, we are interested in the functional significance of interactions between S-layers and other components of the cell envelope.
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