Activation sites of wild-type and mutant mPlg. A. SDS-PAGE of wild-type and mutant mPlm activated with SAK. Standard molecular weight is indicated on the right side. The number system for each mutant and the wild-type is labeled at the top, and is the same for Table 2. In addition, mutations for each lane are labeled at the top of the figure with single amino acid letters. The two bands (15.0 and 10.2 KD) from the major non-specific activation site at position K698 of the wild-type enzyme are highlighted at the left side of the figure. These two bands are not present in mutant lanes. After activation at the R561 site (shown in C) for both wild-type and the mutants, two major bands (25.2 and 13.3 KD) appear and are indicated with dots at the left side of the band. Molecular weights of other minor, non-specific cleavage bands are also labeled at the left. B. Purified SAK (16 KD) used in this experiment. C. Schematic presentation of the cleavage sites derived from A. The activation site at R561 is shown for both the wild-type and the mutants. The top scheme shows the cleavage pattern for the wild-type mPlm, which includes a major non-specific cleavage site at K698, and two of the minor non-specific cleavage sites. The bottom scheme shows the cleavage pattern for the mutants, in which the K698 position is no longer cleavable.