The Transposon-Like Correia Elements Encode Numerous Strong Promoters and Provide a Potential New Mechanism for Phase Variation in the Meningococcus
Figure 1
The eight classes of the consensus CE.
(A) Nucleotide sequence alignment of the 8 CE consensus subtypes. Dashes within the alignment indicate gaps. Asterisks mark the positions of the R and Y nucleotides where the consensus sequence is polymorphic. “R” represents either A or G, with adenosine more frequently present at this position. “Y” represents T, or more frequently C. Nucleotides are colored according to their identity except for the two polymorphisms and the flanking TA dinucleotide repeats, which are black. The CE −10 and −35 transcriptional start sequences and the equivalent sequences for the consensus E. coli σ70 promoter are indicated below the alignment. The total number of elements of each subclass within the N. meningitidis Z2491, MC58 and FAM18 genomes is indicated beside the alignment. These numbers represent approximately half of the total number of elements present in the 3 genomes. (B) Alignment of the α and β TIRs from the left and right ends of the CE. Asterisks mark the 2 nucleotides within the inverted repeat that differ between the left and right ends. The CE −10 and −35 transcriptional start sequences are underlined. For comparison purposes, the −10 and −35 transcriptional start sequences of the consensus E. coli σ70 promoter are provided below the alignment. Also given are the mutated −10 and −35 sequences constructed to replace the wild-type sequences in the Correia end-lacZ reporter plasmids in Table 1. (C) A graphical illustration of sequence variation, relative to the consensus sequence, within the set of 121 α-α CEs.