Uncoupling the MgATP-induced inhibition and aggregation of Escherichia coli phosphofructokinase-2 by C-terminal mutations.

Binding of MgATP to an allosteric site of Escherichia coli phosphofructokinase-2 (Pfk-2) provoked inhibition and a dimer-tetramer (D-T) conversion of the enzyme. Successive deletions of up to 10 residues and point mutations at the C-terminal end led to mutants with elevated K(Mapp) values for MgATP which failed to show the D-T conversion, but were still inhibited by the nucleotide. Y306 was required for the quaternary packing involved in the D-T conversion and the next residue, L307, was crucial for the ternary packing necessary for the catalytic MgATP-binding site. These results show that the D-T conversion could be uncoupled from the conformational changes that lead to the MgATP-induced allosteric inhibition.

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