Recombinant human tau isoforms 2N4R, 0N4R (4R) and 0N3R (3R) were tested for binding to GST-Hsc70 using GST protein as a negative control (lanes 1–9). Protein complexes were resolved by SDS-PAGE and tau binding was confirmed by immunoblotting. As controls, top and bottom panels in lanes 7 and 8 show the GST proteins as detected by anti-GST. Lanes 10 and 11 test the association between 3R tau and two deletion mutants of GST-Hsc70 that lack hsc70 carboxy-terminal sequence; the two truncated GST-Hsc70 proteins were detected by anti-GST (lanes 10 and 11, top panel). Full length hsc70 bound all wild-type tau isoforms tested (lanes 1, 4, 7) while two hsc70 deletion mutants lacking carboxy-terminal sequence did not bind tau (lanes 10 and 11, middle panel). Some recombinant protein preps showed some degradation, as in lanes 3 and 7. Input lanes depict the tau input: lane 3 = 10% (50 ng); lane 6 = 0.5% (1 ng); lane 9 = 1% (2 ng).