The outer membrane of gram-negative bacteria such as E.coli acts as a selective permeability barrier and prevents uncontrolled exchange of solutes and nutrients such as sugars, nucleotides, amino acids and ions. Uptake of these substances is highly controlled by channel- forming integral membrane proteins known as outer-membrane porins (1). Outer membrane proteins, for example the outer membrane protein G (OmpG), are actively forming pores in their target membrane and enable the exchange of soluble molecules through the membrane. Structural insides into these pore-forming proteins enable their manipulation and control. Integration of such controllable pores into natural or artificial membranes allows their application as controllable, selective filters and analytical tools.
Scientists from the Max-Planck-Institute of Biophysics in Frankfurt a. M. have determined the major amino acids at the opening and closing loop (L6) of the outer membrane protein G (OmpG) that are assessable via mutagenesis (1). This allows the opening and closing mechanisms of this pore-building protein to be controlled by e.g. increasing or reducing the pH conditions, or, dependent on the amino acid substitutions, by the presence and coupling of specific metal ions. The scientists have build an artificial (lipid) membrane which contains OmpGs with a specific controllable function enabling for example, the detection and exact quantification of ions, carbohydrates or other molecules. In addition, the membrane can be coupled to functional gold electrodes to build a selective electrode.
Artificial membranes containing mutated and thus assessable pore-forming proteins can be used
European patent has been granted in DE and AT in 2011. First filing date was in 2006.Literature
Yildiz et al., EMBO Journal (2006) 25, 3702–3713. doi:10.1038/ sj.emboj.7601237