Coexistence of the genes for putrescine transport protein and ornithine decarboxylase at 16 min on Escherichia coli chromosome

• Published in: The Journal of biological chemistry 1991-11, Vol.266 (31), p.20922-20927
• Main Authors: Kashiwagi, K., Suzuki, T., Suzuki, F., Furuchi, T., Kobayashi, H., Igarashi, K.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Antiporters; Bacterial Proteins - genetics; Base Sequence; Binding and carrier proteins; Biological and medical sciences; Chromosome Mapping; Chromosomes, Bacterial - ultrastructure; Cloning, Molecular; DNA, Bacterial - genetics; Escherichia coli - enzymology; Escherichia coli - genetics; Escherichia coli Proteins; Fundamental and applied biological sciences. Psychology; genes; Genes, Bacterial; Membrane Proteins - genetics; Molecular Sequence Data; Molecular Weight; Operon; ornithine decarboxylase; Ornithine Decarboxylase - genetics; Proteins; Putrescine - metabolism; putrescine transporter; Restriction Mapping; Solubility
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)54798-0

The nucleotide sequence of one of the putrescine transport operons (pPT71), located at 16 min of the Escherichia coli chromosome, was determined. It contained the genes for an induced ornithine decarboxylase and a putrescine transport protein. The gene for the ornithine decarboxylase contained a 2,196-nucleotide open reading frame encoding a 732-amino acid protein whose calculated Mr was 82,414, and the predicted amino acid sequence from the open reading frame had 65% homology with that of a constitutive ornithine decarboxylase encoded by the gene at 64 min. The ornithine decarboxylase activity was observed in the cells carrying pPT71 cultured at pH 5.2, but not in the cells cultured at pH 7.0. The gene for the putrescine transport protein contained a 1,317-nucleotide open reading frame encoding a 439-amino acid protein whose calculated Mr was 46,494. The hydropathy profile of the putrescine transport protein revealed that it consisted of 12 putative transmembrane spanning segments linked by hydrophilic segments of variable length. The transport protein was in fact found in the membrane fraction. When the gene for the putrescine transport protein was linked to the tet promoter of the vector instead of its own promoter, the putrescine transport activity increased greatly. The results suggest that the gene expression of the operon is repressed strongly under standard conditions.