Translational order of bovine leukemia virus gag and env gene-coded proteins

The translational orders of bovine leukemia virus (BLV) gag proteins and env proteins have been determined by the technique of pactamycin mapping. BLV-producing fetal lamb kidney (FLK) cells were pulse-labeled with 14C amino acids and [3H]glucosamine in the presence or absence of pactamycin which inhibits initiation of protein synthesis but not elongation. Viruses were harvested from the cell culture medium and viral proteins were analyzed by SDS-polyacrylamide gel electrophoresis. For each protein the " pactamycin ratio" was determined. The lower this ratio was for a given protein, the closer the protein would be to the amino terminus of the precursor polyprotein. From these experiments the following translational orders were derived: gag, NH2-p10-(p15(2) X p15(1)-p24-p12-COOH; and env, NH2- gp64 - gp30 -COOH. Investigation of isoelectric points of BLV proteins, a conserved property of retroviral proteins, supported the translational order of gag gene-coded proteins.