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. 2014 Apr 25;9(4):e95188. doi: 10.1371/journal.pone.0095188

Figure 3. Substrate-dependent effects of sodium chloride on the catalytic activity of LcA.

Figure 3

The 30-µl reaction mixtures containing 0.2 mg/ml BSA, 12 µM SNAP25 or 66-mer substrate +1.0 nM LcA, or 0.5 mM 17-mer substrate +50 nM LcA in 50 mM Na-HEPES, pH 7.4. The choice of 50-fold difference in LcA concentration was based on the fact that the SNAP25 substrate concentration used was 42-fold lower than the 17-mer substrate because of a ∼45-fold difference in the Km of SNAP25 or its 66-mer with the 17-mer (see later in Table 3). The SNAP25 and 66-mer substrate reaction mixtures also contained 5 mM DTT, and 250 µM ZnCl2, and the reactions were allowed to proceed for 10 min, while the 17-mer reaction was allowed to proceed for 5 min. Addition of 5 mM DTT and 250 µM ZnCl2 to the 17-mer substrate reactions yielded results identical to those without them as shown in this figure.