Fig. 4.

Synthetic peptides based on the 38/42 processing sites in the 3D7 and Wellcome-type MSP1 are poor substrates for PfSUB1.RP-HPLC chromatograms showing partial digestion by rPfSUB1 of N-acetylated decapeptides based on the primary processing sites in the Wellcome-type (A–C) and 3D7-type (D) MSP1. The top chromatogram in each panel shows the elution profile of an equimolar mix of the undigested peptides, while the lower chromatogram shows the RP-HPLC elution profile after partial digestion with rPfSUB1. Identities of major peaks as determined by electrospray mass spectrometry (data not shown but see Koussis et al., 2009), are indicated. As described previously (Yeoh et al., 2007; Koussis et al., 2009), highly polar cleavage products were usually not retained by the RP-HPLC column but eluted in the column flow-through. Note that for determination of relative initial rates of cleavage, cleavage rates were compared when the faster-cleaved peptide of each pair was digested by ≤ 10%, as described in Experimental procedures. For clarity, digestion was allowed to proceed much more than 10% in most of the profiles shown in this figure.