Ion binding induces closed conformation in Pseudomonas 7A glutaminase-asparaginase (PGA): crystal structure of the PGA-SO4(2-)-NH4+ complex at 1.7 A resolution.Jakob, C.G., Lewinski, K., LaCount, M.W., Roberts, J., Lebioda, L.
(1997) Biochemistry 36: 923-931
- PubMed: 9020792
- DOI: 10.1021/bi961979x
- PubMed Abstract:
- Refined Crystal Structure of Acinetobacter Glutaminasificans Glutaminase-Asparaginase
Lubkowski, J.,Wlodawer, A.,Housset, D.,Weber, I.T.,Ammon, H.L.,Murphy, K.C.,Swain, A.L.
() TO BE PUBLISHED --: --
- A Left-Handed Crossover Involved in Amidohydrolase Catalysis. Crystal Structure of Erwinia Chrysanthemi L-Asparaginase with Bound L-Aspartate
Miller, M.,Rao, J.K.,Wlodawer, A.,Gribskov, M.R.
(1993) FEBS Lett. 328: 275
- Crystal Structure of Escherichia Coli L-Asparaginase, an Enzyme Used in Cancer Therapy
Swain, A.L.,Jaskolski, M.,Housset, D.,Rao, J.K.,Wlodawer, A.
(1993) Proc.Natl.Acad.Sci.USA 90: 1474
Pseudomonas 7A glutaminase-asparaginase (PGA) catalyzes the hydrolysis of D- and L-isomers of glutamine and asparagine. X-ray quality type-1 crystals of PGA have been obtained from 2.0 M ammonium sulfate. The space group is C222(1) with unit-cell dim ...
Pseudomonas 7A glutaminase-asparaginase (PGA) catalyzes the hydrolysis of D- and L-isomers of glutamine and asparagine. X-ray quality type-1 crystals of PGA have been obtained from 2.0 M ammonium sulfate. The space group is C222(1) with unit-cell dimensions a = 78.62, b = 135.80, and c = 137.88 A. The tetrameric molecule is located on a crystallographic 2-fold axis, and two subunits form the asymmetric portion of the unit cell. The structure was solved by the molecular replacement method and refined at 1.7 A resolution to an R = 19.9% with a good geometry of the model, G = 0.05. The resultant electron density maps enabled us to resolve individual constituent atoms of most residues and introduce minor revisions to the amino acid sequence. The catalytic loop, Thr20-Gly40, is in the closed conformation with excellent electron density in both subunits. A sulfate ion and an ammonium ion are bound in the substrate binding site and interect with the loop. This interaction appears to be responsible for the observed closed conformation. New arguments supporting Thr20 as the catalytic nucleophile in the asparaginase activity are proposed.
Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA.