Anaerobiospirillum succiniciproducens phosphoenolpyruvate carboxykinase: mutagenesis at metal site 2.
Phosphoenolpyruvate (PEP) carboxykinases harbor two divalent metal-binding sites. One cation interacts with the enzyme (metal binding site 1) to elicit activation, while a second cation (metal binding site 2) interacts with the nucleotide to serve as the metal nucleotide substrate. Mutants of Anaerobiospirillum succiniciproducens PEP carboxykinase have been constructed where Thr249 and Asp262, two residues of metal binding site 2 of the enzyme, were altered. Binding of the 3'(2')-O-(N-methylantraniloyl) derivative of ADP provides a test of the structural integrity of these mutants. The conservative mutation (Asp262Glu) retains a significant proportion of the wild type enzymatic activity. Meanwhile, removal of the OH group of Thr249 in the Thr249Ala mutant causes a decrease in V(max) by a factor of 1.1 x 10(4). Molecular modeling of wild type and mutant enzymes suggests that the lower catalytic efficiency of the Thr249Ala enzyme could be explained by a movement of the lateral chain of Lys248, a critical catalytic residue, away from the reaction center.
Jabalquinto
Ana María
AM
Departamento de Ciencias Químicas, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile. ajabalqu@lauca.usach.cl
Laivenieks
Maris
M
González-Nilo
Fernando D
FD
Encinas
María Victoria
MV
Zeikus
Gregory
G
Cardemil
Emilio
E
D044044:Aeromonadaceae / Q000201:enzymology* / Q000235:genetics; D001665:Binding Sites; D002942:Circular Dichroism; D003198:Computer Simulation; D007700:Kinetics; D008670:Metals / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D016296:Mutagenesis / Q000235:genetics*; D020125:Mutation, Missense / Q000235:genetics; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017434:Protein Structure, Tertiary
D008670:Metals; D019764:Phosphoenolpyruvate Carboxykinase (ATP)