Autoprocessing of precursors with different N-terminal tags. The GST portion in the GST-p6*-PR-HA construct (Figure 2A) was replaced with a GCN motif (left), GFP (middle), or Hsp70 (right), respectively. The resulting precursors also contained a Flag peptide upstream of the D site. Blots were probed using either mouse anti-Flag (upper) or mouse anti-HA (lower) primary antibodies. The dotted lines connect the products expected from D site cleavage reaction and solid lines connect the products from P site cleavage reaction. The GCN4- containing products were too small to detect by SDS-PAGE.