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Published online on November 12, 2007, 10.1073/pnas.0705768104
PNAS | November 20, 2007 | vol. 104 | no. 47 | 18712-18717


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BIOLOGICAL SCIENCES / MICROBIOLOGY
B1500, a small membrane protein, connects the two-component systems EvgS/EvgA and PhoQ/PhoP in Escherichia coli

Yoko Eguchi*, Junji Itou*, Masatake Yamane*, Ryo Demizu*, Fumiyuki Yamato*, Ario Okada*, Hirotada Mori{dagger}, Akinori Kato*, and Ryutaro Utsumi*,{ddagger}

*Department of Bioscience, Graduate School of Agriculture, Kinki University, 3327-204, Nakamachi, Nara, 631-8505, Japan; and {dagger}Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, 630-0101, Japan

Edited by Eduardo A. Groisman, Washington University, St. Louis, MO, and accepted by the Editorial Board October 3, 2007 (received for review June 20, 2007)

Two-component signal-transduction systems (TCSs) of bacteria are considered to form an intricate signal network to cope with various environmental stresses. One example of such a network in Escherichia coli is the signal transduction cascade from the EvgS/EvgA system to the PhoQ/PhoP system, where activation of the EvgS/EvgA system promotes expression of PhoP-activated genes. As a factor connecting this signal transduction cascade, we have identified a small inner membrane protein (65 aa), B1500. Expression of the b1500 gene is directly regulated by the EvgS/EvgA system, and b1500 expression from a heterologous promoter simultaneously activated the expression of mgtA and other PhoP regulon genes. This activation was PhoQ/PhoP-dependent and EvgS/EvgA-independent. Furthermore, deletion of b1500 from an EvgS-activated strain suppressed mgtA expression. B1500 is localized in the inner membrane, and bacterial two-hybrid data showed that B1500 formed a complex with the sensor PhoQ. These results indicate that the small membrane protein, B1500, connected the signal transduction between EvgS/EvgA and PhoQ/PhoP systems by directly interacting with PhoQ, thus activating the PhoQ/PhoP system.

two-component signal transduction

Author contributions: Y.E. and J.I. contributed equally to this work; R.U. designed research; Y.E., J.I., M.Y., R.D., F.Y., A.O., H.M., and A.K. performed research; and Y.E. and R.U. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission. E.A.G. is a guest editor invited by the Editorial Board.

This article contains supporting information online at www.pnas.org/cgi/content/full/0705768104/DC1.

{ddagger}To whom correspondence should be addressed. E-mail: utsumi{at}nara.kindai.ac.jp

© 2007 by The National Academy of Sciences of the USA


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