Figure 1.

Structural Analyses of Starch-Like Granules Accumulated by the Wild-Type Strain and Class A Mutants.

Insoluble water polysaccharides purified from the wild type (A). A severe mutant 99A7 (C) and an intermediate mutant 153H12 (E) were subjected to size-exclusion chromatography analysis (CL2B sepharose). The wavelength (λ_max, gray lines) at the maximal absorbance (black lines) of the iodine-polysaccharide complex was determined for each fraction. As previously described, starch-like granules of the wild type are composed of semiamylopectin (fractions 9 to 16) and amylose-like polysaccharides (fractions 17 to 27). Both starch-like granules of class A mutants are composed exclusively of abnormal semiamylopectin fraction (λ_max values ranging between 490 and 500 nm instead of 507 nm for the wild-type semiamylopectin). Fractions containing semiamylopectin material were pooled and subjected to chain-length distribution analysis. After complete digestion with commercial isoamylase, chains of Glc were separated according to their DP by HPAEC-PAD. The relative abundance for each DP (gray bars) was determined for the wild type (B), the 99A7 mutant (D), and the 153H12 mutant (F) from three independent extractions. Subtractive analyses (percentage of each DP in the mutant’s semiamylopectin minus percentage of each DP in the wild type’s semiamylopectin), depicted as black lines in (D) and (F), reveal an increase of short chains (DP 3 to 10) and a decrease in long-chain content (DP 12 to 35) in the severe mutant 99A7 (in [D]) and no significant difference in the intermediate 153H12 mutant (in [F]).