Team:TU Eindhoven/Background/Membrane Anchors

Membrane Anchors: OmpX and Penn Anchor

To be able to click molecules over the entire cell surface, a protein to anchor the desired coating to the cell is needed. This protein has to be modified in such a way that it contains an azide displayed on the outside of the cell, where it can react with a DBCO-conjugate. Check also our SPAAC Reaction Page for detailed information.

Membrane Anchor Protein CPX

OmpX (Outer Membrane Protein X) is a small, monomeric β-barrel protein that is highly expressed and very useful for protein display applications in E. coli. CPX (Circularly Permuted OmpX) was developed as a bacterial display methodology for N- and C-terminal display. It demonstrated to enable rapid screening of very large peptide libraries with high precision and efficiency. OmpX possesses four extracellular loops, with loops 2 and 3 forming a semi rigid β-sheets protruding from the cell surface. The native N- and C-termini were fused together by a GGSG-linker, and the newly formed N- and C-termini reside on the cell surface. This makes insertion of an unnatural amino acid fairly easy as it can be positioned before the N-terminus or after the C-terminus. By doing this, the protein itself does not have to be modified. See Figure 1 for a schematic overview of CPX and OmpX.

Figure 1. Structure of OmpX alongside a topological depiction of OmpX and CPX.