Coordinate expression of a small polypeptide with the lactose carrier of Escherichia coli.
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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Lagarias
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Villarejo
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D007158:Immunologic Techniques; D007763:Lac Operon; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D027981:Symporters; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D027981:Symporters; C021499:lactose permease