Revised sequence of the nusA gene of Escherichia coli and identification of nusA11 (ts) and nusA1 mutations which cause changes in a hydrophobic amino acid cluster.

The mutant nusA DNAs (nusA11 and nusA1) were sequenced. Single base substitutions caused by these mutations were found in the coding region of nusA. The nusA11 mutation, which is conditionally lethal, substituted Thr for the 181st Ala. Also, nusA1, which restricts λ growth, substituted Ala for the 183rd Ser. These two positions were located in the same hydrophobic amino acid cluster. This cluster seemed to be an essential region in the functional domain of NusA. In the course of these experiments, several mistakes in the published nusA nucleotide sequence were found. These errors are revised in this article. The molecular weight of NusA is accordingly revised to 54,430.