Regulation and expression of human Fabs under the control of the Escherichia coli arabinose promoter, P-BAD

Background: The L-arabinose operon from E. coli contains an inducible promoter P-BAD which has been extensively studied for the control of gene expression, P-BAD has a number of potential advantages over P-lac, and has been used successfully to promote high level expression of recombinant proteins. Objectives: The aim of this study was to investigate P-BAD as an alternative system to P-lac for the bacterial expression of recombinant Fabs, Study design: The promoter P-BAD from the E. coli arabinose operon araBAD and the gene encoding the regulator of this promoter, were cloned into the phagemid expression vector MCO1. Expression of human recombinant tetanus toroid (TT) and c-erbB2 Fabs under the control of P-BAD was compared at two induction temperatures with the same Fabs produced under the control of P-lac. Results: Expression of TT and c-erbB2 Fabs under the control of P-BAD was comparable to Fab expression from P-lac. However, highly expressed TT Fab under the control of P-BAD was localised to the soluble periplasmic fraction whereas under the control of P-lac, there was greater leakage of Fab into the culture supernatant. In addition, Fab expression from P-BAD could be more tightly repressed than from P-lac. Conclusion: P-BAD is a useful and cheaply inducible alternative to the more commonly used P-lac for the rapid expression of soluble recombinant human antibody fragments. (C) 1997 Elsevier Science B.V.