title: Structural characterization of glutamine synthetase from Azospirillum brasilense.
abstract: CD spectroscopic study of the secondary structure of partly adenylylated glutamine synthetase (GS) of the bacterium Azospirillum brasilense showed both the native and cation-free (EDTA-treated) enzyme to be highly structured (58 and 49% as alpha-helices, 10 and 20% as beta-structure, respectively). Mg(2+), Mn(2+), or Co(2+), when added to the native GS, had little effect on its CD spectrum, whereas their effects on the cation-free GS were more pronounced. Emission ((57)Co) Mössbauer spectroscopic (EMS) study of (57)Co(2+)-doped cation-free GS in frozen solution and in the dried state gave similar spectra and Mössbauer parameters for the corresponding spectral components, reflecting the ability of the Co(2+)-enzyme complex to retain its properties upon drying. The EMS data show that (a) A. brasilense GS has 2 cation-binding sites per active center and (b) one site has a higher affinity to Co(2+) than the other, in line with the data on other bacterial GSs.
authors.affiliation: Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, 410049 Saratov, Russia. aakamnev@ibppm.sgu.ru
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Kamnev
authors.forename: Lyudmila P
authors.initials: LP
authors.lastname: Antonyuk
authors.forename: Victoria E
authors.initials: VE
authors.lastname: Smirnova
authors.forename: Leonid A
authors.initials: LA
authors.lastname: Kulikov
authors.forename: Yury D
authors.initials: YD
authors.lastname: Perfiliev
authors.forename: Irina A
authors.initials: IA
authors.lastname: Kudelina
authors.forename: Erno
authors.initials: E
authors.lastname: Kuzmann
authors.forename: Attila
authors.initials: A
authors.lastname: Vértes
mesh_terms: D016949:Azospirillum / Q000201:enzymology; D015806:Azospirillum brasilense / Q000201:enzymology*; D002412:Cations; D002942:Circular Dichroism; D003035:Cobalt / Q000737:chemistry; D005974:Glutamate-Ammonia Ligase / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D002412:Cations; D003035:Cobalt; D005974:Glutamate-Ammonia Ligase; D008274:Magnesium