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Journal of Bacteriology, April 2009, p. 2776-2782, Vol. 191, No. 8
0021-9193/09/$08.00+0 doi:10.1128/JB.01314-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Yuichi Tsuboi,1
Shinpei Oda,1
Hyeon Guk Kim,1
Hidehiko Kumagai,2 and
Hideyuki Suzuki3*
Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan,1 Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi-cho, Ishikawa-gun, Ishikawa 921-8836, Japan,2 Division of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Goshokaido-cho, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan3
Received 17 September 2008/ Accepted 25 January 2009
The Puu pathway is a putrescine utilization pathway involving gamma-glutamyl intermediates. The genes encoding the enzymes of the Puu pathway form a gene cluster, the puu gene cluster, and puuP is one of the genes in this cluster. In Escherichia coli, three putrescine importers, PotFGHI, PotABCD, and PotE, were discovered in the 1990s and have been studied; however, PuuP had not been discovered previously. This paper shows that PuuP is a novel putrescine importer whose kinetic parameters are equivalent to those of the polyamine importers discovered previously. A puuP+ strain absorbed up to 5 mM putrescine from the medium, but a
puuP strain did not. E. coli strain MA261 has been used in previous studies of polyamine transporters, but PuuP had not been identified previously. It was revealed that the puuP gene of MA261 was inactivated by a point mutation. When E. coli was grown on minimal medium supplemented with putrescine as the sole carbon or nitrogen source, only PuuP among the polyamine importers was required. puuP was expressed strongly when putrescine was added to the medium or when the puuR gene, which encodes a putative repressor, was deleted. When E. coli was grown in M9-tryptone medium, PuuP was expressed mainly in the exponential growth phase, and PotFGHI was expressed independently of the growth phase.
Published ahead of print on 30 January 2009.
Present address: Japan Collection of Microorganisms, Microbe Division, RIKEN, BioResource Center, Wako, Saitama, 351-0198, Japan.
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