Intracellular protein breakdown in growing cells of Escherichia coli

Abstract

When E. coli was grown exponentially in a defined medium at 35 degrees, the rate of protein breakdown was initially rapid, but decreased to 0.6 percent/hr. after about 30 min. The latter rate was maintained for at least 3.5 hr. The initial rapid rate may have been due to the presence of a small protein fraction (about 1 percent) that was degraded with a half-life of 13 min. The rate of protein degradation was the same during balanced growth at low rates imposed in a bactogen. However, it increased during the period immediately after a decrease of the growth rate.