Fig. 5
From: A new class of hybrid secretion system is employed in Pseudomonas amyloid biogenesis
FapD is a periplasmic C39 protease required for FapC secretion. a Comparison of C39 domains in peptidase-containing ATP-binding cassette transporters. b FapD homology model generated by i-Tasser from PDB id 4ry2 (green). The active site His and Cys are conserved and shown in stick representation. c A C38A mutant was unable to secrete FapC fibres demonstrating FapD functions as an active peptidase. Coexpression of the FapD knockout operon with a plasmid encoding wild-type FapD with an OmpA signal sequence restores FapC secretion and confirms FapD is active in the periplasm. The 25 and 50 kDA MW markers are shown. d Mapping of peptides observed in whole-cell lysates of Pseudomonas sp. UK4 expressing the complete fap operon to the Fap protein sequences. Regions with matching peptides are shown as red boxes and the signal peptides, which are absent in the mature proteins, are shown as blue boxes. For additional details, see the Supplementary Data 2. Peptides are observed for FapA–D throughout the sequence indicating no processing. No peptides were observed in the mature N-terminal of FapE, although sequence analysis indicate the possibility for several theoretical peptides of proper size. This indicates a proteolytical processing of FapE. For FapF the disordered linker region residue 60–100 is potentially processed whilst the putative coiled-coil region remains intact.
