Premium
Immunochemical comparison of transformation‐associated protein and secreted phosphoprotein
Author(s) -
Chan James C.,
Scanlon Mike,
Denhardt David T.,
Singh Krishna,
Mukherjee Barid B.,
FarachCarson Mary C.,
Butler William T.
Publication year - 1990
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910460519
Subject(s) - phosphoprotein , methionine , biology , immunoprecipitation , transformation (genetics) , amino acid , microbiology and biotechnology , cell culture , biochemistry , trypsinization , phosphorylation , gene , trypsin , genetics , enzyme
Transformation‐associated protein (TAP) has been detected in MSV‐M‐transformed rat cell lines as glycosylated, weakly phosphorylated protein of molecular weight (M r ) 66,000 and 68,000. In the ts‐MSV‐M‐transformed rat kidney cell line (6m2), the synthesis of TAP and the v‐mos gene product is temperature‐sensitive and accompanies the expression of transformation phenotypes. Therefore, TAP potentially plays a role in cellular transformation. On the other hand, SPP represents a family of glycosylated phosphoprotein with apparent M r ranging from 42,000 to 69,000. SPP has been detected in osteoblasts and in avian and murine retrovirustransformed rat and mouse epithelial cells. Therefore, the potential relatedness of TAP and SPP was studied. Using the 6m2 cells, we found that SPP was strongly phosphorylated and was synthesized at both the permissive (33°C) and nonpermissive (39°C) temperatures. By contrast, TAP was weakly phosphorylated, and was synthesized, as we found previously, only at the permissive temperature of 33°C. Furthermore, in 35 S‐methionine incorporation studies, TAP became heavily labelled whereas SPP was not (consistent with its amino acid composition having few methionine residues). Using 125 I‐TAP in both immunoprecipitation and radioimmunoassays, it was found that an antiserum raised against SPP did not cross‐react with 125 I‐TAP. Additionally, SPP has now been found in many human and rodent cells, while TAP thus far has only been detected in MSV‐transformed rat cells. These data suggest that structurally, TAP and SPP are not closely related phosphoproteins.