TAP purification of Prp8-associated proteins. (A) TAP-purified proteins were fractionated in a 4%–12% PAGE gel and analyzed by mass spectrometry. (B) Effect of salt on the association of the pairs of dissected Prp8 polypeptides. Splicing extracts were incubated with IgG-agarose in the presence of 150, 300, or 500 mM NaCl. Proteins were fractionated, blotted, and probed with anti-8.6 antibodies. (Lanes 1) Nontagged full-length Prp8p, (lanes 2) Tap-tagged full-length Prp8p, (lanes 3) TAP-tagged Prp8p dissected at residue 770, (lanes 4) TAP-tagged Prp8p dissected at residue 2173.