Stability analysis of various VipA mutants and their effect on VipB stability. Left panel: The intrabacterial stability of His6-tagged VipA mutants was examined. At time 0, chloramphenicol was added to stop new protein synthesis. Samples from pelleted bacteria were taken at different time points, and the amount of VipA protein was detected by western blot using anti-His antibodies. Right panel: The impact on VipB expression/stability exhibited by the various vipA mutants was investigated by western blot using anti-VipB antibodies.