An avian leukosis group-specific antigen (gs-a) was isolated from Tween-ether treated avian myeloblastosis virus (AMV) by cellulose acetate electrophoresis. Antigen and protein moved as a single component on Sephadex G-100 column chromatography and on polyacrylamide gel electrophoresis at pH 4.3 and 8.5. Calibration with proteins of known molecular weight of the Sephadex G-100 column and the pH 8.5 gel [containing 0.1% sodium dodecyl sulfate (SDS)] allowed estimation of the molecular weight of the antigen as about 20,000, consistent with earlier studies using ultracentrifugation. The N-terminal amino acid was determined by digestion of the protein with leucine aminopeptidase and by reaction with 14C-labeled fluorodinitrobenzene (FDNB) and 35S-labeled phenylisothiocyanate (PITC). All results indicated that proline was an N-terminal group. Using 35S-PITC, it was shown that there was one N-terminal proline per mole of gs-a.
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1 Support was provided cer Society, Inc., Grant Atomic Energy Contract 2 This is publication Commission of Harvard