PelB secretion signal derived from pectate lyase of <i>Erwinia carotovora</i> (<i>E. carotovora</i>) promotes an efficient secretion of <i>Gaussia princeps</i> luciferase (Gluc) by <i>E. coli</i>.

<p>M: lane for protein marker, B: whole <i>E. coli</i> cell lysate before induction with IPTG, A: whole cell lysate after induction, T: total whole cell lysate after French press lysis, S: soluble fraction of lysate after French press, I: insoluble fraction of lysate after French press. Arrow: the predicted position of Gluc-HlyA on gel. Asterisk: the predicted position of Gluc, PelB-Gluc, and SS-Gluc fusion protein. For panel A and B, lysate corresponding to 10⁸ cells was loaded in each lane. (A) The expression of Gluc without secretion signal (Gluc) or Gluc with C-terminal secretion signal derived from α-hemolysin (Gluc-HlyA) was induced from pCOLDI-based vectors in <i>E. coli.</i> Expressions were detected by Western blotting using a rabbit polyclonal antibody against Gluc. (B) The expression of Gluc with N-terminal secretion signal derived from pectate lyase (PelB-Gluc) or Gluc with its native secretion signal from <i>Gaussia princeps</i> (SS-Gluc) was induced from pCOLDI-based vectors in <i>E. coli</i> and detected by the above rabbit polyclonal antibody. (C) For panel C, the bacterial culture supernatant corresponding to secreted protein from 2×10⁸ cells was loaded in each lane. −: Culture supernatant of <i>E. coli</i> expressing Gluc without secretion signal, H: supernatant of <i>E. coli</i> expressing Gluc-HlyA, P: supernatant of <i>E. coli</i> expressing pelB-Gluc, +: supernatant of <i>E. coli</i> expressing SS-Gluc. Note: The exposure time for panel A and B was shorter than for panel C. There is a gel crack in the lane of “+” which appears two bands at the position of SS-Gluc.