Tau is a microtubule-associated protein expressed primarily in neurons.  Carboxy-terminal domains of Tau associate with and stabilize microtubule structure, while other domains bind to the plasma membrane.  Abnormal Tau phosphorylation can result in the self-assembly of tangles of paired helical and/or straight filaments, which are involved in the pathogenesis of Alzheimer's disease and other neurodegenerative diseases.  Properly folded Tau is highly soluble, but when the protein becomes misfolded it forms insoluble aggregates that can damage cytoplasmic functions, interfere with axonal transport and ultimately lead to cell death.  There are multiple isoforms of Tau—this 410 amino acid isoform is known as “2N3R,” “Isoform Tau-C,” “Tau-3,” or “Tau 410” and is referenced in UniProt as P10636-5.  This recombinant protein is untagged.