Preliminary crystal structure of Acinetobacter glutaminasificans glutaminase-asparaginase.
The preliminary structure of a glutaminase-asparaginase from Acinetobacter glutaminasificans is reported. The structure was determined at 3.0-A resolution with a combination of phase information from multiple isomorphous replacement at 4-5-A resolution and phase improvement and extension by two density modification techniques. The electron density map was fitted by a polypeptide chain that was initially polyalanine. This was subsequently replaced by a polypeptide with an amino acid sequence in agreement with the sizes and shapes of the side chain electron densities. The crystallographic R factor is 0.300 following restrained least squares refinement with data to 2.9-A resolution. The A. glutaminasificans glutaminase-asparaginase subunit folds into two domains: the aminoterminal domain contains a five-stranded beta sheet surrounded by five alpha helices, while the carboxyl-terminal domain contains three alpha helices and less regular structure. The connectivity is not fully determined at present, due in part to the lack of a complete amino acid sequence. The A. glutaminasificans glutaminase-asparaginase structure has been used successfully to determine the relative orientations of the molecules in crystals of Pseudomonas 7A glutaminase-asparaginase, in crystals of Vibrio succinogenes asparaginase, and in a new crystal form of Escherichia coli asparaginase (space group 1222, one subunit per asymmetric unit).
Ammon
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HL
Department of Chemistry and Biochemistry, University of Maryland, College Park 20742.
Weber
I T
IT
Wlodawer
A
A
Harrison
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RW
Gilliland
G L
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Murphy
K C
KC
Sjölin
L
L
Roberts
J
J
D000150:Acinetobacter / Q000201:enzymology*; D000581:Amidohydrolases / Q000302:isolation & purification / Q000378:metabolism; D001215:Asparaginase / Q000378:metabolism; D003460:Crystallization; D004926:Escherichia coli / Q000201:enzymology; D046911:Macromolecular Substances; D008958:Models, Molecular; D011487:Protein Conformation; D011549:Pseudomonas / Q000201:enzymology; D013329:Structure-Activity Relationship; D014733:Vibrio / Q000201:enzymology; D014961:X-Ray Diffraction
D046911:Macromolecular Substances; D000581:Amidohydrolases; D001215:Asparaginase; C020654:glutamin-(asparagin-)ase