Fig 2.

Signal peptide substrates of different classes of signal peptidases. Schematic representations are shown for bacterial (Sec-type) signal peptides cleaved by SPI, twin-arginine (Tat) signal peptides cleaved by SPI, lipoprotein signal peptides cleaved by SPII, bacterial prepilin signal peptides cleaved by SPIV, and archaeal preflagellin signal peptides cleaved by the SPIV homologue FlaK. The N, H, C, and basic regions of the respective signal peptides, mature protein parts, and conserved SP recognition sites are indicated. The SP cleavage site is marked with a black arrowhead. N, N terminus; C, C terminus.