Assembly of colicin genes from a few DNA fragments. Nucleotide sequence of colicin D.
The nucleotide sequence of a 2.4 kb Dral-EcoRV fragment of pColD-CA23 DNA was determined. The segment of DNA contained the colicin D structural gene (cda) and the colicin D immunity gene (cdi). From the nucleotide sequence it was deduced that colicin D had a molecular weight of 74,683 D and that the immunity protein had a molecular weight of 10,057 D. The amino-terminal portion of colicin D was found to be 96% homologous with the same region of colicin B. Both colicins share the same cell-surface receptor, FepA, and require the TonB protein for uptake. A putative TonB box pentapeptide sequence was identified in the amino terminus of the colicin D protein sequence. Since colicin D inhibits protein synthesis, it was unexpected that no homology was found between the carboxy-terminal part of this colicin and that of the protein synthesis inhibiting colicin E3 and cloacin DF13. This could indicate that colicin D does not function in the same manner as the latter two bacteriocins. The observed homology with colicin B supports the domain structure concept of colicin organization. The structural organization of the colicin operon is discussed. The extensive amino-terminal homology between colicins D and B, and the strong carboxy-terminal homology between colicins B, A, and N suggest an evolutionary assembly of colicin genes from a few DNA fragments which encode the functional domains responsible for colicin activity and uptake.
Roos
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Mikrobiologie II, Universität Tübingen, FRG.
Harkness
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Braun
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D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003087:Colicins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D008970:Molecular Weight; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid
D000596:Amino Acids; D001426:Bacterial Proteins; C488854:Cbi protein, E coli; D003087:Colicins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C488855:ceiC protein, E coli; C007104:colicin immunity proteins