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Characterization of single-chain antibody (sFv)-toxin fusion proteins produced in vitro in rabbit reticulocyte lysate.

Research output: Contribution to Journal/MagazineJournal article

  • P. J. Nicholls
  • V. G. Johnson
  • H. R. Hoogenboom
  • J. C. M. Raus
  • R. J. Youle
<mark>Journal publication date</mark>1993
<mark>Journal</mark>Journal of Biological Chemistry
Issue number7
Number of pages7
Pages (from-to)5302-5308
Publication StatusPublished
<mark>Original language</mark>English


Chimeric proteins consisting of a fusion between binding-deficient mutants of diphtheria toxin (DT) or Pseudomonas exotoxin A (PE) and a single-chain antibody (E6 sFv) against the human transferrin receptor (TfnR) were expressed in a rabbit reticulocyte lysate system. Molecules utilizing PE40 (the carboxyl terminus 40 kDa of PE, lacking the binding domain) exhibited significant E6 sFv-mediated, cell type-specific cytotoxicity (IC50 1 x 10(-10) M) against a human erythroleukemia- derived cell line, K562. In contrast, a fusion protein between the same sFv and a DT mutant, DTM1 (containing two amino acid substitutions in the binding domain [S(508)F, S(525)F]) was not significantly cytotoxic, despite being enzymatically active. A tripartite protein in the form NH2-DTM1-E6 sFv-PE40-COOH exhibited cytotoxicity comparable to that of the PE40-sFv fusion (IC50 1 x 10(-10) M), suggesting that the deficit in activity of DTM1-sFv is not a function of misfolding of the sFv moiety or of a reduced ability to bind TfnR. In contrast to DTM1-E6 sFv, a fusion protein between a second DT mutant, CRM 107 [S(525)F], and the E6 sFv was specifically cytotoxic (IC50 1 x 10(-9) M), and toxicity could be blocked by addition of excess E6 antibody. The cell- free in vitro expression system we describe is rapid and may be used to express functional toxin-sFv fusion proteins. No protein refolding procedures are required, and the technique may be used to express proteins which, due to restrictions imposed on manipulation of toxin- encoding genes in Escherichia coli, could not be produced by more conventional methods.