Specific high affinity binding of human interleukin 1β by Caf1A usher protein of Yersinia pestis

Understanding the interaction of Yersinia pestis with the key components of the immune system is important for elucidation of the pathogenesis of bubonic plague, one of the most severe and acute bacterial diseases. Here we report the specific, high affinity binding ( K d = 1.40 × 10 −10 M ± 0.14 × 10 −10) of radiolabelled human interleukin 1β (hIL-1β) to E. coli cells carrying the capsular fl operon of Y. pestis. Caf1A outer membrane usher protein was isolated to greater than 98% purity. Competition studies with purified Caf1, together with immunoblotting studies, identified Caf1A as the hIL-1β receptor. Competition between Caf1 subunit and hIL-1β for the same or an overlapping binding site on CaflA was demonstrated. Relevance of these results to the pathogenesis of Y. pestis and other Gram negative bacterial pathogens with homologous outer membrane usher proteins is discussed.