StpA stability in Lon-protease-deficient E. coli. Measurement of StpA stability in JGJ220 (hns+, lon+), JGJ221 (hns, lon+), JGJ222 (hns+, lon), and JGJ223 (hns, lon) strains. The relative amount of StpA was monitored by Western blotting after protein synthesis was inhibited.