Phos-tag diagonal electrophoresis precisely detects the mobility change of phosphoproteins in Phos-tag SDS-PAGE

摘要

Phos-tag diagonal electrophoresis was developed to identify precisely a change in electrophoretic mobility of phosphoproteins in Phos-tag SDS-PAGE. Previously, if a single protein band was detected, it was impossible to determine whether mobility of the protein altered by Mn2+ Phos-tag in Phos-tag SDS-PAGE gels because SDSPAGE and Phos-tag SDS-PAGE were performed on different gels. Moreover, when multiple protein bands were detected, it was difficult to determine whether the band with the highest mobility was altered mobility by Mn2+ Phos-tag. However, these problems were resolved by Phos-tag diagonal electrophoresis in which SDSPAGE and Phos-tag SDS-PAGE patterns were provided on a single gel. Using this technique we identified phosphorylation states of various proteins such as alpha-lactalbumin, alpha and beta-casein, ovalbumin, basic 7S globulin, and 26S proteasome subunits. In the analyses of 26S proteasome subunits from humans and yeast, we could confirm that all subunits are phosphorylated, and find that the number of major proteins with different phosphorylation states is a few in each of the subunits despite having many phosphorylation sites.