Tau 2: A Probe for a Ser Conformation in the Amino Terminus of τ

Abstract: We have determined the epitope for Tau 2, a monoclonal antibody that intensely stained tangles, plaque neurites, and curly fibers in the tissue section, and strongly labeled bovine τ, but only very weakly labeled human r on the blot. The epitope has been localized to Ala⁹⁵ through Ala¹⁰⁸ of bovine τ. Ser¹⁰¹ is critical for Tau 2 reactivities; the replacement of Ser by Pro, which is found in rat, mouse, and human T, brings about very weak Tau 2 reactivities. The strong Tau 2 staining of tangles and its effective absorption with a synthetic Ser peptide (Ala⁹⁵ through Ala¹⁰⁸) suggest that the τ in paired helical filaments takes a Ser conformation, rather than a Pro conformation, in its ammo‐terminal portion.