Cloning and sequence of the crp gene of Escherichia coli K 12.

We have determined the nucleotide sequence of the crp gene of Escherichia coli K 12. From a lambda transducing phage, the crp region was subcloned into pBR322. The gene was localized on the cloned fragment by determining the length of deletions which affect its expression. Its nucleotide sequence was established by using the technique of Maxam and Gilbert. The deduced amino-acid sequence is in agreement with the previously published amino acid composition of the protein (1, 2). Analysis of the sequence confirms that the DNA binding domain is located in the C-terminal portion of the protein

crp genes of Shigella flexneri, Salmonella typhimurium, and Escherichia coli.

The complete nucleotide sequences of the Salmonella typhimurium LT2 and Shigella flexneri 2B crp genes were determined and compared with those of the Escherichia coli K-12 crp gene. The Shigella flexneri gene was almost like the E. coli crp gene, with only four silent base pair changes. The S. typhimurium and E. coli crp genes presented a higher degree of divergence in their nucleotide sequence with 77 changes, but the corresponding amino acid sequences presented only one amino acid difference. The nucleotide sequences of the crp genes diverged to the same extent as in the other genes, trp, ompA, metJ, and araC, which are structural or regulatory genes. An analysis of the amino acid divergence, however, revealed that the catabolite gene activator protein, the crp gene product, is the most conserved protein observed so far. Comparison of codon usage in S. typhimurium and E. coli for all genes sequenced in both organisms showed that their patterns were similar. Comparison of the regulatory regions of the S. typhimurium and E. coli crp genes showed that the most conserved sequences were those known to be essential for the expression of E. coli crp