Structural characterization of glutamine synthetase from Azospirillum brasilense.
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.
Kamnev
Alexander A
AA
Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, 410049 Saratov, Russia. aakamnev@ibppm.sgu.ru
Antonyuk
Lyudmila P
LP
Smirnova
Victoria E
VE
Kulikov
Leonid A
LA
Perfiliev
Yury D
YD
Kudelina
Irina A
IA
Kuzmann
Erno
E
Vértes
Attila
A
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
D002412:Cations; D003035:Cobalt; D005974:Glutamate-Ammonia Ligase; D008274:Magnesium