On the role of protein phosphorylation in the ATP‐dependent permeabilization of transformed cells

Gary A. Weisman, Stanley D. Dunn, Barun K. De, Takayuki Kitagawa, Ilan Friedberg

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Incubation of transformed mouse fibroblasts with external ATP in alkaline medium low in divalent cations causes an increase in the permeability of the plasma membrane to nucleotides and other small molecules. Previous suggestions that the phosphorylation of a 44,000 dalton membrane protein is involved in this permeabilization process have been pursued. Fractionation of cells that had been incubated with [γ‐32P] ATP revealed that the labeled 44K phosphoprotein was found in both the membrane and mitochondrial fractions. Incubation of fractions isolated from unlabeled cells with [γ‐32P] ATP resulted in substantial formation of 32P‐44K in the mitochondrial fraction and less incorporation in the membrane fraction. The 44,000 dalton protein was identified as the α‐subunit of mitochondrial pyruvate dehydrogenase by partial proteolytic mapping and immunological cross‐reactivity with antibodies prepared against bovine pyruvate dehydrogenase. The phosphorylation of this protein in whole cells by externally added ATP is suppressed by inclusion in the incubation medium of carboxyatractyloside (CAT) and EDTA. These substances have no effect on ATP‐dependent permeabilization, indicating that the phosphorylation of pyruvate dehydrogenase is not involved in this process.

Original languageEnglish (US)
Pages (from-to)124-132
Number of pages9
JournalJournal of Cellular Physiology
Issue number2
StatePublished - Feb 1984

ASJC Scopus subject areas

  • Physiology
  • Clinical Biochemistry
  • Cell Biology


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