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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Glycine 122 is essential for cooperativity and binding of Mg2+ to porcine fructose-1,6-bisphosphatase.

Site-directed mutagenesis of an amino acid residue in the substrate binding site of porcine fructose-1,6-bisphosphatase was carried out based on the crystal structure of the enzyme (Zhang, Y., Liang, J.-Y., Huang, S., Ke, H., and Lipscomb, W. N. (1993) Biochemistry 32, 1844-1857). A mutant enzyme form of fructose-1,6-bisphosphatase, G122A, was purified and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, circular dichroism spectrometry (CD), and initial rate kinetics. There were no discernible differences between the secondary structures of the wild-type and the mutant enzyme on the basis of CD data. Altering Gly-122 to alanine caused a significant decrease in the enzyme's activity and affinity for Mg2+. The kcat for this mutant enzyme was only about 5% of that of wild-type fructose-1,6-bisphosphatase, and the Ka for Mg2+ was about 20-fold higher than that of the wild-type enzyme. The Ki for AMP was increased 77-fold in the case of the mutant enzyme; however, the Hill coefficient was unaltered. Most importantly, it was observed that replacement of Gly-122 with alanine caused the total loss of cooperativity for Mg2+. It is concluded that Gly-122 is essential for Mg2+ cooperativity and important for binding of Mg2+ and AMP as well as for enzyme activity.[1]

References

  1. Glycine 122 is essential for cooperativity and binding of Mg2+ to porcine fructose-1,6-bisphosphatase. Zhang, R., Chen, L., Villeret, V., Fromm, H.J. J. Biol. Chem. (1995) [Pubmed]
 
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