PURIFICATION AND PARTIAL CHARACTERIZATION OF A PRENEOPLASTIC ANTIGEN IN LIVER CARCINOGENESIS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 40  (10) , 3755-3762
Abstract
A preneoplastic antigen was isolated from the microsomal fraction of the hyperplastic nodules of rat liver. During the purification, the presence of preneoplastic antigen was monitored by microcomplement fixation test and double immunodiffusion plate following reaction with antiserum specific for this antigen. The antigen was purified. It migrated as a single protein band in nondenaturing and denaturing polyacrylamide gel electrophoresis, showed a single sharp peak in an isoelectric focusing column at pH 4.75 and had a single serine amino-terminal amino acid. In the absence of detergent during purification, this protein tends to form molecular aggregates. It appears to be a glycoprotein based on the positive periodic acid-Schiff stain and absorption by concanavalin A: Sepharose affinity column chromatography. Amino acid analysis indicated that the protein is acidic, having acidic amino acids (aspartate and glutamate) and basic amino acids (lysine, arginine and histidine) in a ratio of 6.8. An estimate of the MW by gel filtration gave a value of 145,000 and a calculated Stokes radius of 41.5 .ANG.. Electrophoresis under denaturing conditions on sodium dodecyl sulfate-polyacrylamide gel indicated that this protein is a dimer consisting of 2 subunits of equal MW (74,000). Circular dichroism spectra indicated .alpha.-helix contents at 298 and 222 nm of 25.5 and 28.3%, respectively. A similar protein is present in the endoplasmic reticulum of normal rat liver, but in a much lower concentration.