Cloning and promoter identification of the iron-regulated cir gene of Escherichia coli.
The cir gene, which encodes the colicin I receptor protein and is regulated by both cellular iron content and growth temperature, was cloned into a multicopy-number plasmid. Physical mapping and complementation analysis established the position of cir between mgl and nfo on the Escherichia coli chromosome. A gene encoding a 32,000-dalton polypeptide was located downstream of and adjacent to cir, but did not appear to be part of the same transcriptional unit. A 525-base-pair fragment from the 5' end of the 1.8-kilobase-pair receptor-coding region directed iron-regulated transcription and translation of a hybrid cir-lacZ gene. Two overlapping promoters were identified by determination of the transcriptional start sites and by sequence analysis. A small open reading frame (120 nucleotides) of unknown significance preceded the receptor-coding sequence. Examination of the amino acid sequence of the receptor purified from the outer membrane revealed that the gene product was processed by removal of a signal peptide and that the mature form had an amino acid sequence near its amino terminus which closely resembled that of several other TonB-dependent proteins.
Griggs
D W
DW
Department of Microbiology, University of Illinois, Urbana 61801.
Tharp
B B
BB
Konisky
J
J
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003087:Colicins / Q000235:genetics; D003360:Cosmids; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D005786:Gene Expression Regulation; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D007501:Iron / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals / Q000235:genetics; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic / Q000235:genetics*; D013696:Temperature; D014158:Transcription, Genetic
D001425:Bacterial Outer Membrane Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; D021382:Protein Sorting Signals; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; C028593:colicin receptor, E coli; D007501:Iron