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Interaction of calmodulin with the phosphofructokinase target sequence.
Stephen R Martin1, Rodolfo R Biekofsky, Murray A Skinner
1Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
FEBS Letters
|November 6, 2004
Summary
Calcium-bound calmodulin (Ca4.CaM) inhibits glycolysis by blocking phosphofructokinase
Area of Science:
- Biochemistry
- Molecular Biology
- Enzyme Regulation
Background:
- Calmodulin (CaM) is a crucial calcium-binding protein involved in cellular signaling.
- Ca4.CaM, the calcium-saturated form of calmodulin, regulates various cellular processes.
- Phosphofructokinase (PFK) is a key regulatory enzyme in the glycolytic pathway.
Purpose of the Study:
- To investigate the pH-dependent interaction between Ca4.CaM and its target peptide.
- To elucidate the molecular mechanisms underlying Ca4.CaM's inhibition of phosphofructokinase.
Main Methods:
- Fluorescence titrations to determine binding affinity.
- 1H NMR pH titration to analyze histidine pKa changes.
- HSQC spectra to assess pH-dependent conformational changes.
Main Results:
- Ca4.CaM binding affinity to the target peptide increased 1000-fold from pH 9.0 to 4.8.
- Evidence suggests involvement of histidine and carboxylic acid residues in binding.
- NMR data revealed a significant increase in peptide histidine pKa and pH-dependent conformational changes in the complex.
Conclusions:
- The Ca4.CaM-target peptide interaction is highly sensitive to pH.
- This pH sensitivity suggests a regulatory role for Ca4.CaM in the glycolytic pathway.
- Understanding these interactions could reveal novel therapeutic targets for metabolic disorders.