Heterotropic interactions of AMP and glucose binding sites in phosphorylase a are destroyed by limited proteolysis

Pál Gergely, Béla Tóth, Viktor Dombrádi, János Matkó, György Bot

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Subtilisin BPN' hydrolyses a single peptide bond in phosphorylase a. The two proteolytic fragments are attached to each other by noncovalent bonds in solution as shown by gel filtration and ultracentrifugation studies. The subtilisin nicked phosphorylase a is inactive, however, still binds AMP and glucose as judged by equilibrium dialysis and fluorescence experiments. The modified enzyme can be dephosphorylated by protein phosphatase and AMP is an effective inhibitor of the dephosphorylation reaction. Glucose cannot cancel the AMP inhibition as well as cannot expel AMP from the nucleotide binding site. Thus a single nick in the polypeptide chain breaks the "communication" between the two ligand binding domains.

Original languageEnglish
Pages (from-to)825-831
Number of pages7
JournalBiochemical and biophysical research communications
Issue number3
Publication statusPublished - Jun 29 1983


ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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