title: Influence of divalent cations on the catalytic properties and secondary structure of unadenylylated glutamine synthetase from Azospirillum brasilense.
abstract: Fully unadenylylated glutamine synthetase (GS) from the endophytic bacterium Azospirillum brasilense Sp245 was isolated and purified. The enzyme was electrophoretically homogeneous and contained strongly bound metal ions, which 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 the A. brasilense GS is a highly structured protein: 59% of its residues form 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 enzyme secondary structure.
authors.affiliation: Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, Saratov. antonyuk@ibppm.saratov.su
authors.forename: L P
authors.initials: LP
authors.lastname: Antonyuk
authors.forename: V E
authors.initials: VE
authors.lastname: Smirnova
authors.forename: A A
authors.initials: AA
authors.lastname: Kamnev
authors.forename: O B
authors.initials: OB
authors.lastname: Serebrennikova
authors.forename: M A
authors.initials: MA
authors.lastname: Vanoni
authors.forename: G
authors.initials: G
authors.lastname: Zanetti
authors.forename: I A
authors.initials: IA
authors.lastname: Kudelina
authors.forename: O I
authors.initials: OI
authors.lastname: Sokolov
authors.forename: V V
authors.initials: VV
authors.lastname: Ignatov
mesh_terms: D000249:Adenosine Monophosphate / Q000737:chemistry; D015806:Azospirillum brasilense / Q000201:enzymology*; D002384:Catalysis; D002413:Cations, Divalent / Q000494:pharmacology; D002942:Circular Dichroism; D005974:Glutamate-Ammonia Ligase / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D017433:Protein Structure, Secondary / Q000187:drug effects
chemical_list: D002413:Cations, Divalent; D000249:Adenosine Monophosphate; D005974:Glutamate-Ammonia Ligase