ABSTRACT
Analysis of the posttranslational modification of proteins, such as phosphorylation,might yield misleading results due to the presence of other proteins with similar electrophoreticproperties that coimmunoprecipitate with the target protein. The aim ofthe present work was to develop a reliable, easy and economical technique to completelyisolate a protein from its complex. Here we present a new assay developed tofully isolate proteins from macromolecular complexes that consists of an initialSDS/PAGE (under reducing conditions), which isolates the target protein, followedby transfer of the proteins to a buffer, from which the target protein is recaptured byconventional immunoprecipitation. This technique, that we have termed ProteinComplex Immunological Separation Assay (ProCISA), successfully separated proteinsof different sizes, such as pp60Src and the IP3 receptor (IP3R), from their complexes.We show that ProCISA allows the investigation of the tyrosine phosphorylationstate of isolated proteins. This technique could also be used to study other posttranslationalmodifications without risk of misleading results resulting from contaminationwith other proteins of similar electrophoretic mobility which complex with theprotein of interest (AU)
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