Figure 1: Amino acid sequence of proteins secreted by four arthropod-borne pathogens (F. tularensis, Y. pestis, B. bacilliformis, and P. falciparum) with cysteine residues (shaded in gray) confined to the predicted signal peptide segment (boxed italics) of their precursors. Signal peptide excision sites were identified using the SMART online tool. The number of cysteine residues present in the signal peptide segments shown varies from one in F. tularensis lipoprotein to four in P. falciparum blood stage antigen. The mature proteins produced following the removal of signal peptide segments during the secretion process are free of cysteine residues.