Characteristics of Membrane Protein Phosphorylation in Plasmodium berghei‐Infected Mouse Erythrocytes1

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Abstract
Membrane protein phosphorylation in Plasmodium berghei-infected erythrocytes was studied by incubating intact cells with (32P)orthophosphate and incubating isolated membrane with (.gamma.-32P)ATP. Phosphorylated proteins were detected by autoradiography after sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis or isoelectric focusing followed by gel electrophoresis. New phosphorylated proteins were found in membrane from infected erythrocytes, including a protein with electrophoretic mobility identical to band 5, with Mr 43,000. The molar ratio of phosphate to protein ranged between 0.1 and 0.5. Isoelectric focusing-SDS polyacrylamide gel electrophoresis, peptide mapping, extractability properties, and reduction of susceptibility to DNase I inhibition suggested that this protein is phosphorylated actin. In contrast, spectrin phosphorylation in infected erythrocytes was mostly unchanged.