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Journal of Bacteriology, May 2007, p. 3452-3461, Vol. 189, No. 9
0021-9193/07/$08.00+0 doi:10.1128/JB.01751-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

and
Harris D. Bernstein*
Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0538
Received 14 November 2006/ Accepted 15 February 2007
Gram-negative bacteria contain multiple secretion pathways that facilitate the translocation of proteins across the outer membrane. The two-partner secretion (TPS) system is composed of two essential components, a secreted exoprotein and a pore-forming ß barrel protein that is thought to transport the exoprotein across the outer membrane. A putative TPS system was previously described in the annotation of the genome of Escherichia coli O157:H7 strain EDL933. We found that the two components of this system, which we designate OtpA and OtpB, are not predicted to belong to either of the two major subtypes of TPS systems (hemolysins and adhesins) based on their sequences. Nevertheless, we obtained direct evidence that OtpA and OtpB constitute a bona fide TPS system. We found that secretion of OtpA into the extracellular environment in E. coli O157:H7 requires OtpB and that when OtpA was produced in an E. coli K-12 strain, its secretion was strictly dependent on the production of OtpB. Furthermore, using OtpA/OtpB as a model system, we show that protein secretion via the TPS pathway is extremely rapid.
Published ahead of print on 23 February 2007.
Present address: Alcon Laboratories, Inc., 6201 South Freeway, Fort Worth, TX 76134.
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