Western blot of formaldehyde-cross-linked Y. pestis strains KIM6+ (Hms+), KIM6-2118 (ΔhmsR), KIM6-2119 (ΔhmsS), KIM6-2051 (hmsT : : mini-kan) and KIM6-2090.2+ (ΔhmsP) probed with HmsF antisera. Except for one Hms+ control (Hms+ UX), all samples were cross-linked (X) with formaldehyde. Black arrows identify the cross-linked HmsH–HmsF complex, while the grey arrow identifies the HmsF monomer.