Autodisplay: functional display of active beta-lactamase on the surface of Escherichia coli by the AIDA-I autotransporter

Members of the protein family of immunoglobulin A1 protease-like autotransporters comprise multidomain precursors consisting of a C-terminal autotransporter domain that promotes the translocation of N-terminally attached passenger domains across the cell envelopes of gram-negative bacteria. Several autotransporter domains have recently been shown to efficiently promote the export of heterologous passenger domains, opening up an effective tool for surface display of heterologous proteins. Here we report on the autotransporter domain of the Escherichia coli adhesin involved in diffuse adherence (AIDA-I), which was genetically fused to the C terminus of the periplasmic enzyme beta-lactamase, leading to efficient expression of the fusion protein in E. coli. The beta-lactamase moiety of the fusion protein was presented on the bacterial surface in a stable manner, and the surface-located beta-lactamase was shown to be enzymatically active. Enzymatic activity was completely removed by protease treatment, indicating that surface display of beta-lactamase was almost quantitative. The periplasmic domain of the outer membrane protein OmpA was not affected by externally added proteases, demonstrating that the outer membranes of E. coli cells expressing the beta-lactamase AIDA-I fusion protein remained physiologically intact.