Relationships of gp70 of MuLV envelopes to gp70 components of mouse lymphocyte plasma membranes

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Abstract
The family of glycoproteins called gp70 includes molecules that are the main constituent of murine C-type viral envelopes, and some that are expressed as mendelian constituents of thymocyte plasma membranes in the absence of virions. To investigate further the relation of viral gp70s to plasma-membrane gp70s, the peptide maps of gp70s derived by immunoprecipitation from cells infected with chosen viruses and from various thymocytes and leukemia cells known to express 1 or more of 3 immunogenetically defined gp70 types: GIX-gp70, X-gp70 and O-gp70 were compared. Maps of gp70 from cultured cells infected with ecotropic and xenotropic viruses were distinguishable from one another. They resembled gp70 maps prepared directly from ecotropic and xenotropic virions, respectively. Maps of gp70s immunoprecipitated from thymocytes of 5 mouse strains and from 2 A strain T-cell leukemias also fell into 2 distinguishable and generally corresponding patterns. Peptide-mapping substantiates earlier conclusions that viral gp70s and plasma-membrane gp70s inherited independently of virus-production are highly related or identical molecules. The gp70 maps of thymocytes from B6, .**GRAPHIC**. 129 and A mice formed a group resembling the map from cultured cells infected with venotropic virus. Thymocytes from AKR mice, and the 2 A strain leukemias, gave gp70 maps conforming more to the 2nd pattern, that of cultured cells infected with ecotropic virus. This 2nd pattern probably comprises at least 2 gp70 types, 1 of which is X-gp70. The GIx-gp70 and O-gp70 sub-species of gp70 expressed in the cell populations studied are probably coded by xenotropic viral genomes. X-gp70 is probably coded by ecotropic viral genomes.

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