Purification of the wt-A1 fusion protein.

Wild-type A1, prepurified with glutathione-Sepharose beads, was dialyzed (24 hours, 4°C) against 20 mM Tris-HCl, pH 8.0 buffer containing 50 mM NaCl and loaded onto a Q-Sepharose column. (A) wt-A1 was eluted with a 50- to 500-mM NaCl gradient and collected as indicated. (B) SDS-PAGE and silver staining analysis of the collected wt-A1. Lane 1: prepurified wt-A1 after elution from the glutathione-Sepharose beads; lane 2: wt-A1 eluted from the Q-Sepharose. The fusion protein exhibits an apparent M_r of 49 kDa, which increases to 56 kDa after reduction with 100 mM DTE (lane 3).