Figure 4. PCAT1 and LahT147 share common features in substrate recognition.

(A) Insertion of three hydrophobic residues onto a hydrophobic groove on the surface of the PEP domain, represented as electrostatic potential surfaces. CtA is shown in blue and the LahT147 substrate in gold. (B) A conserved hydrophobic knot. (C) Residue at position −4 of the substrate conferring specificity. (D) Pulldown of the wt or mutant CtA using PCAT1(C21A) conjugated resin. The CtA constructs contain a 3x Flag tag at their C-terminus. Western blot was performed using the anti-Flag M2 antibody. (E) Pulldown of PCAT1(C21A) using the M2 antibody resin against the Flag-tagged CtA. Mutation of hydrophobic residue A55 and I59 were introduced to PCAT1(C21A) background. IgG HC and IgG LC denote the heavy chain and the light chain of the M2 antibody, respectively.