Analysis of SSIII activity. A, Two-dimensional zymogram analysis. Proteins from equivalent fresh weights of leaves of wild-type (top) and Atss3-1 (bottom) plants were separated by anion-exchange chromatography. Proteins in equivalent volumes of the indicated HiTrapQ column fractions were separated in native polyacrylamide gels containing 0.3% glycogen, then stained with iodine solution. Identifiable SS activity bands are indicated. The asterisk in the Atss3-1 analysis indicates the position that corresponds to band A in the wild-type analysis. B, Immunoblot analysis. Duplicate gels to those shown in (A) were probed for the presence of SSIII with α-AtSSIII monoclonal antibody. C, One-dimensional zymogram analysis. Total soluble protein extracts from leaves of wild-type, Atss3-1, and Atss3-2 plants were analyzed for SS activity as described for (A). In this instance, there was no prior anion-exchange fractionation step.