Figure 6.

Detection of Stisa Proteins and Isoamylase Activity in Ammonium Sulfate Fractions of Crude Soluble Extracts of Tubers.

Proteins precipitating at ammonium sulfate concentrations of 0 to 20% (lane 1), 20 to 30% (lane 2), 30 to 40% (lane 3), and 40 to 50% (lane 4) saturation were redissolved and subjected to electrophoresis either on a native, amylopectin-containing gel that was stained subsequently with iodine solution (left gel) or on SDS–polyacrylamide gels that were blotted subsequently onto nitrocellulose. Blots were developed with antisera raised to synthetic peptides unique to Stisa1, Stisa2, or Stisa3 (at dilutions of 1:10,000 [Stisa1 and Stisa3] or 1:20,000 [Stisa2]). Lanes 1 to 4 contain protein from the four ammonium sulfate precipitates. Each lane contains the same fraction of the precipitated protein. M indicates molecular mass markers. The arrow on the native gel indicates the position of the blue band of isoamylase activity. Arrows on the protein gel blots indicate the positions of the Stisa1, Stisa2, and Stisa3 peptides detected by the antisera.