Previous genetic and biochemical studies indicate that the carB gene of Escherichia coli codes for the large subunit of carbamoyl-phosphate synthetase (EC 22.214.171.124). We have determined the nucleotide sequence of a 4-kilobase-pair cloned fragment of E. coli DNA with genetic determinants for carB. The DNA sequence is a 3,219-nucleotide-long reading frame. The polypeptide encoded by this reading frame has been verified to be the large subunit of carbamoyl-phosphate synthetase. The gene product is similar to the large subunit in its molecular weight, amino acid composition and amino-terminal residue, and carboxyl-terminal sequence. The amino acid sequence derived from the nucleotide sequence shows a highly significant homology between the amino- and carboxyl-terminal halves of the protein. We propose that the carB gene was formed by an internal duplication of a smaller ancestral gene.
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - 1983 Aug|
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