Structure and function of glutamyl-tRNA reductase,the first enzyme of tetrapyrrole biosynthesis in plants and prokaryotes |
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Authors: | Schubert Wolf-Dieter Moser Jürgen Schauer Stefan Heinz Dirk W Jahn Dieter |
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Institution: | (1) Department of Structural Biology, German Research Center for Biotechnology, Mascheroder Weg 1, 38104 Braunschweig, Germany;(2) Institute of Microbiology, Technical University Braunschweig, Spielmannstrasse 7, 38106 Braunschweig, Germany |
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Abstract: | Glutamyl-tRNA reductase (GluTR) catalyzes the first step of tetrapyrrole biosynthesis in plants, archaea and most bacteria.
The catalytic mechanism of the enzyme was elucidated both by biochemical data and the determination of the high-resolution
crystal structure of the enzyme from the archaeon Methanopyrus kandleri in complex with a competitive inhibitor. The dimeric enzyme has an unusual V-shaped architecture where each monomer consists
of three domains linked by a long `spinal' α-helix. The central catalytic domain specifically recognizes the glutamate moiety
of the substrate. It bears a conserved cysteine poised to nucleophilically attack the activated aminoacyl bond of glutamyl-tRNA.
Subsequently, the thioester intermediate is reduced to the product glutamate-1-semialdehyde via hydride transfer from NADPH
supplied by the second domain. A structure-based sequence alignment indicates that catalytically essential amino acids are
conserved throughout all GluTRs. Thus the catalytic mechanism derived for M. kandleri is common to all including plant GluTRs. Mutations described to influence the catalytic efficiency of the barley enzyme can
therefore be explained.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | catalytic mechanism chlorophyll crystal structure glutamyl-tRNA reductase heme tetrapyrrole biosynthesis |
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