%0 Figure %A Boehlein, Susan K. %A Shaw, Janine R. %A Hannah, L. Curtis %D 2018 %T Image_1_Enhancement of Heat Stability and Kinetic Parameters of the Maize Endosperm ADP-Glucose Pyrophosphorylase by Mutagenesis of Amino Acids in the Small Subunit With High B Factors.JPEG %U https://frontiersin.figshare.com/articles/figure/Image_1_Enhancement_of_Heat_Stability_and_Kinetic_Parameters_of_the_Maize_Endosperm_ADP-Glucose_Pyrophosphorylase_by_Mutagenesis_of_Amino_Acids_in_the_Small_Subunit_With_High_B_Factors_JPEG/7460654 %R 10.3389/fpls.2018.01849.s001 %2 https://frontiersin.figshare.com/ndownloader/files/13814423 %K AGPase (ADP-glucose pyrophosphorylase) %K yield loss at harvest %K heat lability %K climate change %K B-factors %K protein evolution %X

ADP-glucose pyrophosphorylase (AGPase) is an important enzyme in starch synthesis and previous studies showed that the heat lability of this enzyme is a determinant to starch synthesis in the maize endosperm and, in turn, seed yield. Here, amino acids in the AGPase endosperm small subunit with high B-factors were mutagenized and individual changes enhancing heat stability and/or kinetic parameters in an Escherichia coli expression system were chosen. Individual mutations were combined and analyzed. One triple mutant, here termed Bt2-BF, was chosen for further study. Combinations of this heat stable, 3-PGA-independent small subunit variant with large subunits also heat stable yielded complex patterns of heat stability and kinetic and allosteric properties. Interestingly, two of the three changes reside in a protein motif found only in AGPases that exhibit high sensitivity to 3-PGA. While not the 3-PGA binding site, amino acid substitutions in this region significantly alter 3-PGA activation kinetics.

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