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Journal of Bacteriology, December 2001, p. 6943-6946, Vol. 183, No. 23
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.23.6943-6946.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

IS186 Insertion at a Hot Spot in the lon Promoter as a Basis for Lon Protease Deficiency of Escherichia coli B: Identification of a Consensus Target Sequence for IS186 Transposition

L. SaiSree,¹ Manjula Reddy,¹ and J. Gowrishankar^1,2,*

Centre for Cellular and Molecular Biology, Hyderabad 500007,¹ and Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500076,² India

Received 2 July 2001/Accepted 5 September 2001

The radiation sensitivity of Escherichia coli B was first described more than 50 years ago, and the genetic locus responsible for the trait was subsequently identified as lon (encoding Lon protease). We now show that both E. coli B and the first reported E. coli K-12 lon mutant, AB1899, carry IS186 insertions in opposite orientations at a single site in the lon promoter region and that this site represents a natural hot spot for transposition of the insertion sequence (IS) element. Our analysis of deposited sequence data for a number of other IS186 insertion sites permitted the deductions that (i) the consensus target site sequence for IS186 transposition is 5'-(G)₄(N)_3-6(C)₄-3', (ii) the associated host sequence duplication varies within the range of 6 to 12 bp and encompasses the N_(3-6) sequence, and (iii) in a majority of instances, at least one end of the duplication is at the G-N (or N-C) junction. IS186-related sequences were absent in closely related bacterium Salmonella enterica serovar Typhimurium, indicating that this IS element is a recent acquisition in the evolutionary history of E. coli.

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^* Corresponding author. Mailing address: Centre for DNA Fingerprinting and Diagnostics, ECIL Rd., Nacharam, Hyderabad 500076, India. Phone: 91-40-7155609. Fax: 91-40-7155610. E-mail: shankar{at}www.cdfd.org.in.

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Journal of Bacteriology, December 2001, p. 6943-6946, Vol. 183, No. 23
0021-9193/01/$04.00+0   DOI: 10.1128/JB.183.23.6943-6946.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

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