ABSTRACT
A human lung tumor-associated antigen was purified to homogeneity from a crude cell-free extract of a human lung adenocarcinoma using standard biochemical procedures. In order to facilitate monitoring the recovery of antigen, trace amounts of previously purified and radioiodinated antigen from another lung tumor were added to the crude extract. The purified antigen was a glycoprotein and contained sialic acid. The antigen had a molecular weight of 76,000 and appeared to contain three subunits, each with a molecular weight of 25,000. The antigen had the following physical properties: Stokes radius, 39.4 A; S20,w, 4.24 S; D20,w, 5.15 x 10(-7) cm2 S-1; and a frictional ratio of 1.40. In addition, the purified, radioiodinated antigen retained complete immune reactivity since it could be quantitatively precipitated with specific immune serum. All of these properties were in close agreement with the properties of another antigen which was purified from a separate human lung tumor. Thus, it appeared from the biochemical and immunochemical criteria presented in this report that a common and identical antigen was isolated from two distinct human lung tumor extracts.
Subject(s)
Adenocarcinoma/analysis , Antigens, Neoplasm/isolation & purification , Glycoproteins/isolation & purification , Lung Neoplasms/analysis , Adenocarcinoma/immunology , Antigens, Neoplasm/immunology , Cell-Free System , Chromatography, Affinity , Humans , Lung Neoplasms/immunology , Molecular Weight , Neoplasm Metastasis , Sialic Acids/analysisABSTRACT
Human alpha-fetoprotein (hAFP) has been isolated from cord serum in 40% yield using an isolation procedure consisting of only two major steps: affinity chromatography followed by preparative polyacrylamide gel electrophoresis (PAGE). The final product appeared homogeneous on the basis of five independent criteria for purity. Sodium dodecyl sulfate gel electrophoresis (SDS-PAGE) demonstrated a single polypeptide chain with molecular weight of 71,000. The protein exhibited an apparent isoelectric point (pI') of 4.85, molecular radius of 3.0 nm and a valence (net H+/molecule) of 21.9 derived from computation of analytical PAGE data. The two-step isolation procedure made it possible for a single operator to isolate milligram amounts of hAFP in a matter of weeks.
Subject(s)
alpha-Fetoproteins/isolation & purification , Buffers , Chromatography, Affinity/methods , Electrophoresis, Polyacrylamide Gel/methods , Humans , Isoelectric Focusing , Isoelectric Point , Molecular Weight , Protein ConformationABSTRACT
A human lung tumor-associated antigen was purified from a saline extract of a lung adenocarcinoma. The antigen was demonstrated in extracts of lung adenocarcinoma. The antigen was demonstrated in extracts of lung tumors with the use of an absorbed antiserum by double-diffusion immunoprecipitation. The antiserum did not react with extracts of normal lung or other normal tissues, and the antigen was immunologically distinct from other tumor-associated antigens. Purification was achieved by antibody affinity chromatography and preparative polyacrylamide gel electrophoresis. Isolation procedures were monitored by immunoreactivity with absorbed monospecific antiserum. The antigen was labeled with 125I and judged homogeneous by 1) polyacrylamide gel elecrophoresis in detergent and nondetergent gels, 2) molecular sieve chromatography, 3) ion exchange chromatography, and 4) sucrose gradient sedimentation analysis. A molecular weight of 77,000 was calculated from the s20.w value of 4.24S and from the D20.w value of 5.0X10(-7) cm2/sec. Sodium dodecyl sulfate gel electrophoresis indicated a subunit molecular weight of 42,000. The Stokes radius of the antigen was 40 A and the frictional ratio was 1.42, indicating a nonspherical molecule. The purified radioiodinated antigen could be quantitatively precipitated with specific antiserum.
