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TopicPage for oppA 5' UTR of Escherichia coli K-12

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Long 5' UTRs         

Description:

An IS2 insertion at -515 in strain MA261 introduces a strong promoter at the end of IS2, called P1, which initiates transcription three nucleotides past the insertion point, creating a 511 nt 5' UTR in that strain; the parent strain W3110 does not have the IS2 insertion at oppA; in addition to P1, a weak P2 was found at - 266 and a strong P3 was found at -171; both P1 and P3 were inactive when assayed from plasmids; the transcription start points were determined by S1 nuclease mapping; spermidine stimulated transcription from the IS2-encoded promoter but not from the two oppA native chromosomal promoters, which were both inhibited at the level of translation initiation (Igarashi, 1997). MG1655 and MG1655(Seq) do not have the IS2 at oppA; the promoter that was found to initiate a 171 bp 5' UTR is labeled as a promoter for oppA in EcoGene even though the experiments were not done using MG1655 as it seems likely to be an MG1655 promoter since the DNA sequence is exactly the same. Using P3 as the native oppA promoter positions the known Fur binding site at position -53 relative to the transcription start point.

The Sigma28 promoter at -97 relative to the translation start annotated in RegulonDB was not experimentally determined.

Details:

Spermidine binds the 5' UTR of oppA and 145 nt of the oppA ORF to stimulate translation initiation by disrupting a weak hairpin that occludes the oppA RBS (Igarashi, 1997; Igarashi, 2000; Higashi, 2008).

oppA transcription is leucine-responsive (Andrews, 1986; Igarashi, 1997). A putative leucine-responsive element (LRE) predicted at position 1299059-1299070 located within the 5' UTR at -137 (TCACCAGATAA) has not been experimentally proven and does not match the Lrp consensus sequence YAGHAWATTWTDCTR established from 63 random binding sites identied by SELEX (Cui, 1995; Igarashi, 1997).


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