Crystal structure and kinetic analysis of β-lactamase inhibitor protein-II in complex with TEM-1 β-lactamase

The structure of the 28 kDa beta -lactamase inhibitor protein-II (BLIP-II) in complex with the TEM-1 beta -lactamase has been determined to 2.3 Angstrom resolution. BLIP-II is a secreted protein produced by the soil bacterium Streptomyces exfoliatus SMF19 and is able to bind and inhibit TEM-1 with subnanomolar affinity. BLIP-II is a seven-bladed beta -propeller with a unique blade motif consisting of only three antiparallel beta -strands. The overall fold is highly similar to the core structure of the human regulator of chromosome condensation (RCC1). Although BLIP-II does not share the same fold with BLIP, the first beta -lactamase inhibitor protein for which structural data was available, a comparison of the two complexes reveals a number of similarities and provides further insights into key components of the TEM-1-BLIP and TEM-1-BLIP-II interfaces. Our preliminary results from gene knock-out studies and scanning electron microscopy also reveal a critical role of BLIP-II in sporulation.