Abstract
Rat α-fetoprotein (AFP) cDNA spanning the complete coding region was cloned and expressed in Escherichia coli as well as in yeast, Saccharomyces cerevisiae. The recom-binant AFPs (rAFPs) were purified and characterized. The molecular weights determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis were 65, 000 for E. coli rAFP and 69, 000 for yeast rAFP. Amino acid and N-terminal sequence analyses indicated that yeast cells produced mature AFP by processing the signal peptide properly but E. coli rAFP lacked the N-terminal 53 amino acid residues of preAFP. The yeast rAFP was found to be indistinguishable from authentic AFP in the Ouchterlony immunodiffusion test, radioimmunoassay and estradiol-binding assay while E. coli rAFP was less reactive in these tests. These observations indicated that the rAFP expressed in yeast emulated the properties of authentic AFP.
