p56lck protein-tyrosine kinase is cytoskeletal and does not bind to polyomavirus middle T antigen.
p56lck and p60c-src are closely related protein-tyrosine kinases that are activated by similar oncogenic mutations. We have used fibroblast cell lines that express p56lck from introduced DNA molecules to compare the subcellular localizations of p60c-src and p56lck and their abilities to bind polyomavirus middle T antigen (mT). p56lck is associated with the detergent-insoluble matrix, as defined by extraction with solutions containing nonionic detergents, whereas p60c-src is soluble under these conditions. p56lck is also associated with detergent-insoluble structures in a lymphoid cell line, LSTRA. p60c-src binds to mT, but p56lck does not bind detectably. In terms of both solubility and mT interactions, the nononcogenic p56lck more closely resembles oncogenically activated p60c-src mutants than it resembles p60c-src. Because published results show that an intact carboxy terminus is required for p60c-src to bind mT and be soluble, we tested whether the different localization and mT binding properties of p56lck and p60c-src were dictated by their different carboxy termini. A protein consisting largely of p60c-src sequences but carrying a p56lck carboxy terminus was soluble and bound to mT. We suggest that both the solubility and mT-binding properties of p60c-src not only require sequences common to the carboxy termini of p60c-src and p56lck, but also require sequences unique to the body of p60c-src.
Louie
R R
RR
Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
King
C S
CS
MacAuley
A
A
Marth
J D
JD
Perlmutter
R M
RM
Eckhart
W
W
Cooper
J A
JA
D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000378:metabolism*; D001345:Autoradiography; D002460:Cell Line; D002461:Cell Line, Transformed; D002499:Centrifugation, Density Gradient; D002678:Chimera; D003599:Cytoskeleton / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts; D015151:Immunoblotting; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*
D000952:Antigens, Polyomavirus Transforming; D011505:Protein-Tyrosine Kinases