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  • Title: Coordinate expression of a small polypeptide with the lactose carrier of Escherichia coli.
    Author: Lagarias DM, Villarejo M.
    Journal: J Biol Chem; 1985 Nov 15; 260(26):14235-41. PubMed ID: 2414292.
    Abstract:
    Induction of the lac operon in wild type Escherichia coli strains results in synthesis of a 16-kDa inner membrane protein in addition to the known products of the lacZ, lacY, and lacA genes. Cells carrying the lacY gene on a multicopy plasmid overproduce this 16-kDa polypeptide as well as the Lac carrier, the membrane protein product of the lacY gene. However, [35S]methionine labeling of minicells carrying the lacY plasmid shows that the 16-kDa protein is not synthesized from the plasmid DNA. We have purified and partially characterized the 16-kDa protein. It is an acidic membrane protein of apparent Mr = 15,800 whose amino-terminal sequence (NH2-Met-Arg-Asn-Phe-Asp-Leu-) does not match any known lac operon DNA sequence. Using antibody prepared to the purified 16-kDa protein, we have quantitatively analyzed conditions under which this protein is made and have shown that the amount of 16-kDa protein which appears in the membrane is proportional to lac operon expression. Hybridization of a synthetic oligodeoxyribonucleotide probe complementary to the 5' end of 16-kDa protein mRNA shows that its synthesis is regulated at the level of transcription.
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