Localization of the Abelson murine leukemia virus protein in a detergent-insoluble subcellular matrix: architecture of the protein

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Abstract
The interaction of Abelson murine leukemia virus protein P120 with other cellular components was examined after extraction with the nonionic detergent Triton X-100. Most of the Abelson murine leukemia virus P120-associated kinase activity was found in the detergent-insoluble matrix in mouse lymphoid and fibroblast cell lines. The P120 labeled during a short exposure of cells to [35S]-methionine was mainly in the detergent-insoluble matrix (lymphoid cells) or equally distributed in the detergent-insoluble matrix and the soluble fraction (fibroblasts). Steady-state-labeled P120 was distributed equally in the 2 fractions (lymphoid cells) or mostly in the soluble portion (fibroblasts). There was an apparent movement of P120 from the detergent-insoluble matrix to the detergent-soluble fraction and a concomitant loss of enzymatic activity. When the detergent-insoluble matrix was incubated with[32P]ATP in situ, phosphorylation of tyrosine residues of P120 was observed. An 80,000-MW fragment of P120 (designated F80) was found after extraction of fibroblast cells with detergent. F80 was not found in extracted lymphoid cells, but mixing labeled lymphoid cells and unlabeled fibroblasts before extraction produced the fragment. F80 contained the gag determinants of P120 but did not react with Abelson-specific serum. These data allowed assignment of various features of the protein to regions of the P120 molecule and localization of the Abelson-specific antigenic determinants to the C-terminal region of the molecule.