J. Biol. Chem., Vol. 263, Issue 19, 9470-9475, Jul, 1988
Activity of immunotoxins constructed with modified Pseudomonas exotoxin A lacking the cell recognition domain
T Kondo, D FitzGerald, VK Chaudhary, S Adhya and I Pastan
Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland 20892.
Pseudomonas exotoxin (PE) contains three domains whose functions are cell
recognition, membrane translocation, and ADP ribosylation of elongation
factor 2. PE40 is a form of PE which is missing the cell recognition
domain. To study the properties of PE40, it was expressed in Escherichia
coli using a vector which contains a T7 phage promoter, an OmpA signal
sequence, and that portion of the PE gene encoding PE40. Upon induction
with isopropyl-1-thio-beta-D-galactopyranoside, large amounts of PE40 were
secreted, and highly purified PE40 was prepared from the culture medium.
PE40 was chemically coupled to different monoclonal antibodies, and protein
synthesis inhibition activities of these immunotoxins was assessed on
various cell lines. These activities were compared with the activities of
the corresponding immunotoxins made with native PE. These data indicate
that PE40 may be useful in the construction of certain immunotoxins.