Influence of divalent cations on the catalytic properties and secondary structure of unadenylylated glutamine synthetase from Azospirillum brasilense

Authors
Antonyuk, LP Smirnova, VE Kamnev, AA Serebrennikova, OB Vanoni, MA Zanetti, G Kudelina, IA Sokolov, OI Ignatov, VV
Citation
Lp. Antonyuk et al., Influence of divalent cations on the catalytic properties and secondary structure of unadenylylated glutamine synthetase from Azospirillum brasilense, BIOMETALS, 14(1), 2001, pp. 13-22
Citations number
25
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOMETALS
ISSN journal
09660844 → ACNP
Volume
14
Issue
1
Year of publication
2001
Pages
13 - 22
Database
ISI
SICI code
0966-0844(200103)14:1<13:IODCOT>2.0.ZU;2-4
Abstract
Fully unadenylylated glutamine synthetase (GS) from the endophytic bacteriu m Azospirillum brasilense Sp245 was isolated and purified. The enzyme was e lectrophoretically homogeneous and contained strongly bound metal ions, whi ch could not be removed by dialysis. Mn2+, Mg2+, and Co2+ were found to be effective in supporting biosynthetic activity of the A. brasilense GS. Some kinetic properties of Mn2+-activated and Mg2+-activated unadenylylated GS were characterized. Circular dichroism analysis of the enzyme showed that t he A. brasilense GS is a highly structured protein: 59% of its residues for m alpha -helices and 13% beta -strands. Removal of the metal ions from the A. brasilense GS by treatment with EDTA resulted in alterations in the enzy me secondary structure.