Interaction of calmodulin with the phosphofructokinase target sequence.
Ca4.calmodulin (Ca4.CaM) inhibits the glycolytic enzyme phosphofructokinase, by preventing formation of its active tetramer. Fluorescence titrations show that the affinity of complex formation of Ca4.CaM with the key 21-residue target peptide increases 1000-fold from pH 9.0 to 4.8, suggesting the involvement of histidine and carboxylic acid residues. 1H NMR pH titration indicates a marked increase in pKa of the peptide histidine on complex formation and HSQC spectra show related pH-dependent changes in the conformation of the complex. This unusually strong sensitivity of a CaM-target complex to pH suggests a potential functional role for Ca4.CaM in regulation of the glycolytic pathway.
Martin
Stephen R
SR
Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
Biekofsky
Rodolfo R
RR
Skinner
Murray A
MA
Guerrini
Remo
R
Salvadori
Severo
S
Feeney
James
J
Bayley
Peter M
PM
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D004331:Drosophila melanogaster; D006863:Hydrogen-Ion Concentration; D019906:Nuclear Magnetic Resonance, Biomolecular; D025221:Phosphofructokinases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D002147:Calmodulin; D011994:Recombinant Proteins; D025221:Phosphofructokinases; D002118:Calcium