tailieunhanh - Báo cáo khoa học: Complex II from phototrophic purple bacterium Rhodoferax fermentans displays rhodoquinol-fumarate reductase activity

It has long been accepted that bacterial quinol-fumarate reductase (QFR)generally uses a low-redox-potential naphthoquinone, menaquinone (MK), as the electron donor, whereas mitochondrial QFR from facultative and anaerobic eukaryotes uses a low-redox-potential benzoqui-none, rhodoquinone (RQ), as the substrate. In the present study, we purifiednovel complex II fromtheRQ-containing phototrophic purple bacterium,Rhodoferax fermentansthat exhibited high rhodoquinol-fumarate reductase activity in addition to succinate-ubiquinone reductase activity | Eur. J. Biochem. 270 1863-1874 2003 FEBS 2003 doi Complex II from phototrophic purple bacterium Rhodoferax fermentans displays rhodoquinol-fumarate reductase activity Hiroko Miyadera1 Akira Hiraishi2 Hideto Miyoshi3 Kimitoshi Sakamoto3 Reiko Mineki4 Kimie Murayama4 Kenji V. P. Nagashima5 Katsumi Matsuura5 Somei Kojima6 and Kiyoshi Kita1 1 Department of Biomedical Chemistry Graduate School of Medicine The University of Tokyo Japan department of Ecological Engineering Toyohashi University of Technology Japan 3Division of Applied Life Sciences Graduate School of Agriculture Kyoto University Japan division of Biochemical Analysis Central Laboratory of Medical Science Juntendo University School of Medicine Tokyo Japan department of Biology Tokyo Metropolitan University Japan department of Parasitology Institute of Medical Science University of Tokyo Japan It has long been accepted that bacterial quinol-fumarate reductase QFR j ner Ry uses a low-redop-polenlial naphthoquinone menaquinone MK as the electron donor whereas mitochondrial QFR from facultative and anaerobic eukaryotes uses a low-redox-potential benzoquinone rhodoquinone RQ as the substrate. In the present study we purified novel complex II from the RQ-containing phototrophic purple bacterium Rhodoferax fermentans that exhibited high rhodoquinol-fumarate reductase activity in addition to succinate-ubiquinone reductase activity. SDS PAGE indicated that the purified R. fermentans complex II comprises four subunits of and kDa and contains nmol heme per mg protein. Phylogenetic analysis and comparison of the deduced amino acid sequences of R. fermentans complex II with pro eukaryotic complex II indicate that the structure and the evolutional origins of R. fermentans complex II are closer to bacterial SQR than to mitochondrial rhodoquinol-fumarate reductase. The results strongly indicate that R. fermentans complex II and mitochondrial QFR might have evolved .