Evolution of the korA-oriV segment of promiscuous IncP plasmids.
Plasmids belonging to Escherichia coli incompatibility group P are of particular interest because they can transfer between, and be stably maintained in, almost all Gram-negative bacterial species. The segment of the IncP alpha plasmid genome between the key regulatory gene korA and the vegetative replication origin, oriV, encodes a series of operons co-regulated with replication and transfer functions by the KorA protein. To determine which of these genes are likely to have an important role in IncP plasmid survival the equivalent region of the distantly related IncP beta plasmid R751 was sequenced. Sequence comparisons show that the kla operon (formerly the kilA locus, which is also responsible for a cryptic tellurite-resistance determinant) is completely absent from R751. Similarly in the kle region, which encodes genes associated with the KilE+ phenotype of unknown function, kleC and kleD, which we proposed arose by a duplication of kleA and kleB, are also completely absent. The genes that are conserved are klcA (formerly kilC, responsible for the KilC+, and recently proposed to be involved in overcoming restriction barriers during transfer), klcB (an ORF interrupted by Tn1 insertion in RK2), korC (a transcriptional repressor which controls the klcK and kle operons), and kleA, kleB, kleE and kleF. A striking feature of the organization in R751 is the lack of the strong transcriptional termination signals which are present in IncP alpha plasmids. The degree of divergence between the plasmids facilitates the identification of motifs of probable functional importance in the primary protein sequences.
Thomas
Christopher M
CM
School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Smith
Christopher A
CA
School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Ibbotson
John P
JP
School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Johnston
Lynda
L
School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Wang
Naijin
N
School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001483:Base Sequence; D005075:Biological Evolution; D017124:Conserved Sequence; D004261:DNA Replication; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D009876:Operon; D010957:Plasmids; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D001426:Bacterial Proteins; C090051:KorA protein, bacteria; D012097:Repressor Proteins