Abstract
Abnormal tau proteins (PHF-tau) were isolated from Alzheimer's disease brains by treatment of paired helical filament enriched-fractions with perchloric acid and boiling of the acid precipitable fraction with beta-mercaptoethanol. These proteins were purified further by a second perchloric acid treatment. The purified PHF-tau proteins were soluble in buffers devoid of sodium dodecyl sulfate. However, they were similar to the abnormal tau extracted from paired helical filaments with sodium dodecyl sulfate, also named A68, in molecular mass (68, 64, and 60 kDa), isoelectric point (pI 5.5-6.5), reactivity with anti-tau antibodies, and in requirement for alkaline phosphatase treatment to bind the Tau-1 antibody. Compared to normal tau, the soluble PHF-tau contained 100% more glycine and 35% less lysine residue. The results suggest that besides phosphorylation other types of modification may be involved in differentiating PHF-tau from normal tau.
Highlights
Abnormal tau proteins (PHF-tau) were isolated from been referred to asAlzheimer’sdisease proteins (A68) [21] or Alzheimer’s disease brains by treatment of paired hel- TPHF [16]
They were similar to react with all anti-tau antibodies with epitopes spanning the the abnormal tau extracted from paired helical filaments with sodium dodecyl sulfate, alsonamed A68, in molecular mass (68, 64, and 6 0 kDa), isoelectric point (PI 6.6-6.6), reactivity with anti-tau antibodies, and in requirement for alkaline phosphatase treatment to bind the Tau-1 antibody
Tau1, recognizes an epitope encoded by tau gene exon 9 [7], and the other was raised against a synthetic peptide with amino acid sequences encoded by exon 2 [22]
Summary
The SDS-soluble PHF preparations contain aset of proteins with molecular masses of 68, 64, and 60 kDa that are not present in the normal brain tissue. These proteins have previously they may be products of aberrant posttranslational modifications. To study the molecular structure of PHF-tau, and toidentify the modification(s) that distinguishes PHF-tau from normal tau,itis necessary to have highly purified PHF-tau soluble in reagents devoid of SDS. ThePHF-tau were extracted from PHF-enriched samples by heatand acid treatments and were soluble in water or buffers without the need for SDS or other chaotropic agents such as urea or guanidine hydrochloride. $ To whom correspondence should be addressed Dept. of Pathology, F-538 Albert Einstein College of Medicine, 1300 Morris Park
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