Cloning and phylogenetic analysis of the genes encoding acetohydroxyacid synthase from the archaeon Methanococcus aeolicus |
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| Affiliation: | 1. College of Resources and Environment, Hunan Agricultural University, Changsha 410128, People''s Republic of China;2. Hunan Engineering & Technology Research Center for Irrigation Water Purification, Changsha 410128, People''s Republic of China;3. Hunan Engineering Research Center for Safe and High-Efficient Utilization of Heavy Metal Pollution Farmland, Changsha 410128, People''s Republic of China;1. State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China;2. National Institutes for Food and Drug Control, Beijing, 100050, China;3. School of Biological and Chemical Engineering, Zhejiang University of Science and Technology, Hangzhou, 310023, China;4. GeneTalks Biotechnology Inc., Changsha, 410013, China;5. Guangdong Medical Laboratory Technology (Rapid Diagnostic) Engineering Technology Research Center, Guangzhou, 510641, China;6. Guangzhou Wondfo Biotech Co., Ltd., Guangzhou, 510641, China;7. Shanghai Institute of Hematology, State Key Laboratory of Medical Genomics, National Research Center for Translational Medicine at Shanghai, Ruijin Hospital, Shanghai Jiao Tong University of Medicine, Shanghai, 200025, China;1. Department of Chemical Engineering, Cyprus University of Technology, 30 Archbishop Kyprianou Str., 3036, Limassol, Cyprus;3. Department of Mechanical Engineering and Material Science and Engineering, Cyprus University of Technology, 45 Kitiou Kyprianou Str., 3041, Limassol, Cyprus;1. Centro de Astrobiología (CSIC/INTA), Ctra. de Torrejón a Ajalvir km 4, 28850 Torrejón de Ardoz, Spain;2. Ecole Nationale de l’Industrie Minérale, Département des Sciences de la Terre, BP 753 Agdal – Rabat, Morocco;3. Council for Geoscience, P.O. Box 572, Bellville 7535, South Africa;4. United States Geological Survey, P.O. Box 628, Montpelier, VT 05601, USA |
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| Abstract: | The gene for acetohydroxyacid synthase (AHAS) was cloned from the archaeon Methanococcus aeolicus. Contrary to biochemical studies [Xing, R. and Whitman, W.B. (1994) J. Bacteriol. 176, 1207–1213] the enzyme was encoded by two open reading frames (ORFs). Based on sequence homology, these ORFs were designated ilvB and ilvN for the large and small subunits of AHAS, respectively. A putative methanogen promoter preceded ilvB-ilvN, and a potential internal promoter was found upstream of ilvN. ilvB encoded a 65-kDa protein, which agreed well with the measured value for the purified enzyme. ilvN encoded a 19-kDa protein, which fell within the range of Mr of small subunits from other sources. Phylogenetic analysis of the deduced amino acid sequence of ilvB showed a close relationship between the AHAS of Bacteria and Archaea, to the exclusion of other enzymes in this family, including pyruvate oxidase, glyoxylate carboligase, pyruvate decarboxylase, and the acetolactate synthase found in fermentative Bacteria. Thus, this family of enzymes probably arose prior to the divergence of the Bacteria and Archaea. Moreover, the higher plant AHAS and the red algal AHAS were related to the AHAS II of Escherichia coli and the cyanobacterial AHAS, respectively. For this reason, these genes appear to have been acquired by the Eucarya during the endosymbiosis that gave rise to the mitochondrion and chloroplast, respectively. One of the ORFs in the Methanococcus jannaschii genome possesses high similarity to the M. aeolicus ilvB, indicating that it is an authentic AHAS. |
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