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Study of pH- and temperature-induced transitions in F-protein (phosphofructokinase) by spectroscopy and
V L Shnyrov1, N A Freydina, E A Permyakov
1Institute of Biological Physics, U.S.S.R. Academy of Sciences, Pushchino, Moscow Region.
Abstract:
The temperature- and pH-induced transitions in F-protein (phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11] have been studied by means of microcalorimetry and fluorescence and CD spectroscopy. An increase in pH from approx. 6.0 to approx. 8.0 causes a change in the protein state which seems to correspond to a shift of the dimer-tetramer equilibrium in favour of the tetramers. In the absence of phosphate, stability of the protein to temperature- and urea-induced denaturation at pH 6.0 is higher than that at pH 8.0. An addition of 150 mM phosphate results in a pronounced increase in the protein's stability in such a way that the protein becomes more stable at pH 8.0 than at pH 6.0. The shift of the denaturational heat capacity peak induced by the phosphate binding exceeds 25 degrees C at pH 8.0 and 9 degrees C at pH 6.0.