Protein synthesis in Escherichia coli during recovery from exposure to low levels of Cd2+.

Exposure of Escherichia coli to 3 microM Cd2+ results in 84 to 95% of the cells losing their ability to form colonies on plates of nutrient agar. Transfer of the cells to Cd2+-free liquid medium results in a recovery of colony-forming ability without significant synthesis of DNA. As an early event in recovery, the cells exhibit a rapid uptake of [3H]leucine. Recovery and this incorporation are inhibited by chloramphenicol or rifampin. Sodium dodecyl sulfate-gel electrophoresis of proteins from recovering cells labeled with [3H]leucine for 1 min indicated the synthesis of at least two classes of proteins with apparent molecular weights of 55,000 to 65,000. One class bound Cd2+ and was absent in untreated cultures. The other class of proteins, which did not bind Cd2+, was synthesized at a rapid rate in recovering cells and may be a normal cellular protein.