Quaternary structure of Azospirillum brasilense NADPH-dependent glutamate synthase in solution as revealed by synchrotron radiation X-ray scattering
Articolo
Data di Pubblicazione:
2003
Citazione:
Quaternary structure of Azospirillum brasilense NADPH-dependent glutamate synthase in solution as revealed by synchrotron radiation X-ray scattering / M..V. Petoukov, D..I. Svergun, P..V. Konarev, S. Ravasio, R..H..H. van den Heuvel, B. Curti, M.A. Vanoni. - In: THE JOURNAL OF BIOLOGICAL CHEMISTRY. - ISSN 0021-9258. - 278:32(2003), pp. 29933-29939.
Abstract:
Azospirillum brasilense glutamate synthase (GltS) is the prototype of bacterial NADPH-dependent enzymes, a class of complex iron-sulfur flavoproteins essential in ammonia assimilation processes. The catalytically active GltS αβ holoenzyme and its isolated α and β subunits (162 and 52 kDa, respectively) were analyzed using synchrotron radiation x-ray solution scattering. The GltS α subunit and αβ holoenzyme were found to be tetrameric in solution, whereas the β subunit was a mixture of monomers and dimers. Ab initio low resolution shapes restored from the scattering data suggested that the arrangement of a subunits in the (αβ)4 holoenzyme is similar to that in the tetrameric α4 complex and that β subunits occupy the periphery of the holoenzyme. The structure of α4 was further modeled using the available crystallographic coordinates of the monomeric a subunit assuming P222 symmetry. To model the entire αβ holoenzyme, a putative αβ protomer was constructed from the coordinates of the α subunit and those of the N-terminal region of porcine dihydropyrimidine dehydrogenase, which is similar to the β subunit. Rigid body refinement yielded a model of GltS with an arrangement of a subunits similar to that in α4, but displaying contacts also between β subunits belonging to adjacent protomers. The holoenzyme model allows for independent catalytic activity of the αβ protomers, which is consistent with the available biochemical evidence.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
Glutamate synthase, small angle X-ray scattering, amidotransferase
Elenco autori:
M..V. Petoukov, D..I. Svergun, P..V. Konarev, S. Ravasio, R..H..H. van den Heuvel, B. Curti, M.A. Vanoni
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