SKAP-HOM, a novel adaptor protein homologous to the FYN-associated protein SKAP55.
A recombinant GST-Fyn-SH2 domain was used to purify proteins from lysates of pervanadate treated EL4 cells. N-terminal sequencing and molecular cloning of one of the purified polypeptides resulted in the identification of a novel adaptor protein that shares strong structural homology to the recently cloned Fyn-associated adaptor protein SKAP55. This protein was termed SKAP-HOM (SKAP55 homologue). Despite their striking homology, SKAP55 and SKAP-HOM have distinct characteristics. Thus, unlike SKAP55, which is exclusively expressed in T lymphocytes, SKAP-HOM expression is ubiquitous. Furthermore, while SKAP55 is constitutively tyrosine phosphorylated in resting human T cells, SKAP-HOM is expressed as a non-phosphorylated protein in the absence of external stimulus but becomes phosphorylated following T cell activation. In addition, SKAP-HOM does not associate with p59fyn in T cells although it represents a specific substrate for the kinase in COS cells. Finally, we demonstrate that, as previously shown for SKAP55, SKAP-HOM interacts with the recently identified polypeptide SLAP-130.
Ruprecht-Karls University of Heidelberg, Institute for Immunology, Germany. m71@popix.urz.uni-heidelberg.de
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Marie-Cardine
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Verhagen
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Eckerskorn
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Schraven
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000201:enzymology; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D010750:Phosphoproteins; C108336:SKAP1 protein, human; D014443:Tyrosine; D019061:src-Family Kinases