Figure 7.

Sarcosyl-insoluble PHFs contain tyrosine-phosphorylated PHF tau. A, Two micrograms of PHFs were probed with anti-tau (lane 1) or anti-phosphotyrosine mAb4G10 (lane 2); 0.6 μg PHFs were probed with anti-tau (lane 3) or anti-PY18 (lane 4); 0.6 μg PHFs were probed with anti-PY18 after the membrane was incubated with phosphotyrosine-specific protein phosphatase (lane 6). Mock incubation without phosphatase was similarly probed (lane 5). B, PHFs were labeled with PY20 and 10 nm gold-labeled anti-mouse. Labeled filaments were visualized by electron microscopy. Control labeling of the preparation was by 46.1 (top panel). Middle and bottom panels show labeling of nonaggregated (A2) and aggregated (AL2) PHF preparations, respectively (see Materials and Methods).