Differential distribution in white and grey matter of tau phosphoisoforms containing four tubulin-binding motifs

The microtubule-associated protein tau has been isolated and purified from both white and grey brain matter. Tau isoforms were fractionated, based on their different phosphate contents, by iron-chelating affinity chromatography. Differences were observed in the proportions of phosphorylated isoforms of tau protein (containing four tubulin-binding motifs) present in white and grey matter. In white matter, isoforms containing four tubulin-binding motifs are mainly present in a phosphorylated form. Thus there appears to be a correlation between the modification, by phosphorylation, of some sites in the tau molecule and the subcellular localization (axonal or somatodendritic compartments) of the modified isoforms.