Efficient tag-less purification of recombinant human tau proteins.

Tau proteins normally function as part of the neuronal cytoskeleton but aggregate to form filamentous inclusions in tauopathies such as Alzheimer's disease. The diverse functions of tau protein are frequently interrogated using biochemical assays that require highly purified tau as substrate. Conventional recombinant tau purification leverages polyhistidine (His6) tags to enable rapid and efficient isolation through immobilized metal affinity chromatography (IMAC). Preparation of native tau by this approach requires removal of His6 tags through additional processing steps. Here we report a protocol for purifying native recombinant full-length tau protein that retains the speed, convenience, broad availability and scalability of IMAC while eliminating the need for post-purification proteolytic cleavage. The method has been validated across a wide array of tau constructs, including full-length isoforms, missense mutants, and a truncation construct containing an aggregation-prone region of the microtubule-binding domain. Owing to its scalability and reproducibility, the method is well suited for structure-activity relationship investigations involving curated tau variant libraries.