Activation of nonreceptor protein tyrosine kinases ( PTKs ) is essential for T cell receptor ( TCR ) responsiveness ; however , the function of individual PTK substrates is often uncertain .
activation of nonreceptor protein tyrosine kinases ( ptks ) is essential for t cell receptor ( tcr ) responsiveness ; however , the function of individual ptk substrates is often uncertain .
O O B-protein_family_or_group I-protein_family_or_group B-protein_family_or_group I-protein_family_or_group O B-protein_family_or_group O O O O B-protein_family_or_group I-protein_family_or_group I-protein_family_or_group O B-protein_family_or_group O O O O O O O O O B-protein_family_or_group I-protein_family_or_group O O O O