کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2829616 1162818 2006 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The three-dimensional structure of an eukaryotic glutamine synthetase: Functional implications of its oligomeric structure
موضوعات مرتبط
علوم زیستی و بیوفناوری بیوشیمی، ژنتیک و زیست شناسی مولکولی زیست شناسی مولکولی
پیش نمایش صفحه اول مقاله
The three-dimensional structure of an eukaryotic glutamine synthetase: Functional implications of its oligomeric structure
چکیده انگلیسی

The structure of the prokaryotic glutamine synthetases type I (GS-I), key enzymes in nitrogen metabolism, was determined several years ago by X-ray diffraction, and consists of a double hexameric ring. The structure of the eukaryotic GS from the plant Phaseolus vulgaris (Glutamine synthetase type II; GS-II) has now been determined at low-resolution using electron microscopy and image processing, and consists of an octamer composed of two tetramers placed back-to-back and rotated 90° with respect to each other. The oligomeric structure possesses a twofold symmetry, very suggestive of each tetramer being composed of two dimers. This is reinforced by the fact that dimers are isolated as a stable albeit non-functional species during the purification procedure. Given the fact that the active site of all types of GS is formed by highly conserved residues located in the interface of two interacting monomers, the geometry of the reconstructed tetramer suggests that it only contains two functional active sites, i.e., an active site per dimer. This is supported by biochemical data, which reveal that while the octamer binds eight ATP molecules, it only binds four molecules of the transition state analogue and GS inhibitor methionine-(S)-sulfoximine-P (MetSox-P). All this suggests for the GS-II enzyme an oligomeric structure containing four active sites and four possible regulatory sites, which might point to a complex regulatory behavior.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Structural Biology - Volume 156, Issue 3, December 2006, Pages 469–479
نویسندگان
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