J. Biol. Chem., Vol. 266, Issue 18, 11901-11908, Jun, 1991
Yeast expression of a catalytic antibody with chorismate mutase activity
K Bowdish, Y Tang, JB Hicks and D Hilvert
Department of Chemistry, Research Institute of Scripps Clinic, La Jolla, California 92037.
The catalytic antibody 1F7 promotes the rearrangement of chorismate into
prephenate. We cloned and sequenced the genes encoding this catalyst to
determine the origin of the observed rates and specificity. The antibody
cDNAs were modified and inserted into inducible expression vectors.
Simultaneous intracellular expression of the light and truncated heavy
chains in strains of the yeast Saccharomyces cerevisiae lacking natural
chorismate mutase resulted in the production of properly folded and
assembled Fab antibody. Assembly of the light and heavy immunoglobulin
chains is roughly 60-70% efficient in our in vivo system, lagging behind
light chain synthesis throughout log and stationary phase. Nevertheless,
high intracellular levels of functional Fab antibody (0.1% of total
cellular protein) were obtained with an ultra-high copy number plasmid. As
yeast-derived 1F7(Fab) catalyzes the chorismate mutase reaction with the
same specific activity as antibody isolated from the hybridoma, our
expression system now makes possible the application of classical and
"reverse" genetics to the study and improvement of this first-generation
abzyme.