Kurihara Shin, Tsuboi Yuichi, Oda Shinpei, Kim Hyeon Guk, Kumagai Hidehiko, Suzuki Hideyuki
Division of Applied Biology, Graduate School of Science and Technology, Kyoto Institute of Technology, Goshokaido-cho, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan.
J Bacteriol. 2009 Apr;191(8):2776-82. doi: 10.1128/JB.01314-08. Epub 2009 Jan 30.
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 DeltapuuP 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.
Puu途径是一条涉及γ-谷氨酰中间体的腐胺利用途径。编码Puu途径中酶的基因形成一个基因簇，即puu基因簇，而puuP是该簇中的基因之一。在大肠杆菌中，20世纪90年代发现了三种腐胺转运体PotFGHI、PotABCD和PotE，并对其进行了研究；然而，此前尚未发现PuuP。本文表明，PuuP是一种新型腐胺转运体，其动力学参数与之前发现的多胺转运体相当。一个含有puuP(+)的菌株能够从培养基中吸收高达5 mM的腐胺，但缺失PuuP的菌株则不能。大肠杆菌菌株MA261曾用于多胺转运体的先前研究，但此前未鉴定出PuuP。研究发现，MA261的puuP基因因点突变而失活。当大肠杆菌在以腐胺作为唯一碳源或氮源的基本培养基上生长时，多胺转运体中只有PuuP是必需的。当向培养基中添加腐胺或缺失编码假定阻遏物的puuR基因时，puuP会强烈表达。当大肠杆菌在M9-胰蛋白胨培养基中生长时，PuuP主要在指数生长期表达，而PotFGHI的表达与生长阶段无关。
