Intracellular protein breakdown in growing cells of Escherichia coli.

1. When Escherichia coli was grown exponentially in a defined medium at 35 degrees , the rate of protein breakdown was initially rapid, but decreased to 0.6%/hr. after about 30min. The latter rate was maintained for at least 3.5hr. 2. The initial rapid rate may have been due to the presence of a small protein fraction (about 1%) that was degraded with a half-life of 13min. 3. 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.