DNA sequence analysis of the dnaK gene of Escherichia coli B and of two dnaK genes carrying the temperature-sensitive mutations dnaK7(Ts) and dnaK756(Ts).

The DNA sequence of the dnaK gene of Escherichia coli was analyzed. The nucleotide sequence of the wild-type dnaK gene of E. coli B differed from that of E. coli K-12 in 15 bp, none of which altered the amino acid sequence. Two temperature-sensitive dnaK mutations were examined by cloning and sequence analyses. Results showed that one dnaK mutation, dnaK7(Ts), was a one-base substitution of T for C at nucleotide position 448 in the open reading frame yielding an amber nonsense codon. The other mutation, dnaK756(Ts), consisted of base substitutions (A for G) at three nucleotide positions, 95, 1364, and 1403, in the open reading frame resulting in an aspartic acid codon in place of a glycine codon.