Secretion-dependent proteolysis of heterologous protein by recombinant Escherichia coli is connected to an increased activity of the energy-generating dissimilatory pathway.
The synthesis of a proteolytically unstable protein, originally designed for periplasmic export in recombinant Escherichia coli BL21(DE3), a strain naturally deficient for the ATP-dependent protease Lon (or La) and the outer membrane protease OmpT, is associated with a severe growth inhibition. This inhibition is not observed in BL21(DE3) synthesizing a closely related but proteolytically stable protein that is sequestered into inclusion bodies. It is shown that the growth inhibition is mainly caused by a slower cell division rate and a reduced growth yield and not by a general loss of cell division competence. Cells proceed with their normal growth characteristics when exposed again to conditions that do not sustain the expression of the heterologous gene. The performance of cells synthesizing either the stable or the degraded protein was also studied in high cell density cultures by employing a new method to calculate the actual specific growth rate, the biomass yield coefficient, and the dissimilated fraction of the carbon substrate in real-time. It is shown that the growth inhibition of cells synthesizing the proteolytically degraded protein is connected to an increased dissimilation of the carbon substrate resulting in a concomitant reduction of the growth rate and the biomass yield coefficient with respect to the carbon source. It is postulated that the increased dissimilation of the carbon substrate by lon-deficient Bl21(DE3) cells synthesizing the proteolytically unstable protein may result from a higher energy demand required for the in vivo degradation of this protein by ATP-dependent proteases different from the protease Lon.
Schmidt
M
M
GBF National Research Center for Biotechnology, Biochemical Engineering Division, Mascheroder Weg 1, 38124 Braunschweig, Germany.
Viaplana
E
E
Hoffmann
F
F
Marten
S
S
Villaverde
A
A
Rinas
U
U
D049069:ATP-Dependent Proteases; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D019149:Bioreactors; D002244:Carbon / Q000378:metabolism; D002455:Cell Division; D004734:Energy Metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D006360:Heat-Shock Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D002479:Inclusion Bodies; D049070:Protease La; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D015678:Viral Structural Proteins / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D011993:Recombinant Fusion Proteins; D015678:Viral Structural Proteins; C081149:viral protein 60, rabbit hemorrhagic disease virus; D002244:Carbon; D000255:Adenosine Triphosphate; D049069:ATP-Dependent Proteases; D012697:Serine Endopeptidases; C483567:Lon protein, E coli; D049070:Protease La; C057840:omptin outer membrane protease