Protein sequence and mass spectrometric analyses of tau in the Alzheimer's disease brain.
Tau with unusually slow mobilities in sodium dodecyl sulfate-polyacrylamide gel electrophoresis was purified from the Sarkosyl-insoluble pellet of Alzheimer's disease brain homogenates. Such species of tau (PHF-tau) are considered to construct the framework of the sodium dodecyl sulfate-soluble form of paired helical filaments (PHF). Detailed comparison of peptide maps of PHF-tau and normal tau before and after dephosphorylation pointed to three anomalously eluted peaks which contained abnormally phosphorylated peptides, residues 191-225, 226-240, 260-267, and 386-438, according to the numbering of the longest tau isoform (Goedert, M., Spillantini, M. G., Jakes, R., Rutherford, D., and Crowther, R. A. (1989) Neuron 3, 519-526). Protein sequence and mass spectrometric analyses localized Thr-231 and Ser-235 as the abnormal phosphorylation sites and further indicated that each tau 1 site (residues 191-225) and the most carboxyl-terminal portion of the protein (residues 386-438) carries more than two abnormal phosphates. Ser-262 was also phosphorylated in a fraction of PHF-tau. Modifications other than phosphorylation, removal of the initiator methionine, and N alpha-acetylation at the amino terminus and deamidation at 2 asparaginyl residues were found in PHF-tau, but these modifications were also present in normal tau.
Hasegawa
M
M
Department of Neuropathology, Faculty of Medicine, University of Tokyo, Japan.
Morishima-Kawashima
M
M
Takio
K
K
Suzuki
M
M
Titani
K
K
Ihara
Y
Y
D000544:Alzheimer Disease / Q000378:metabolism*; D000595:Amino Acid Sequence; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000302:isolation & purification; D010449:Peptide Mapping; D016875:tau Proteins / Q000737:chemistry* / Q000302:isolation & purification
D010446:Peptide Fragments; D016875:tau Proteins