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Purification and characterization of an activated form of the protein tyrosine kinase Lck from an Escherichia coli expression system
Author(s) -
Flint Nicholas A.,
Amrein Kurt E.,
Jascur Thomas,
Burn Paul
Publication year - 1994
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.240550317
Subject(s) - autophosphorylation , phosphorylation , biochemistry , tyrosine , tyrosine kinase , protein tyrosine phosphatase , biology , sh2 domain , tyrosine phosphorylation , recombinant dna , microbiology and biotechnology , affinity chromatography , signal transduction , enzyme , protein kinase a , gene
The lymphocyte‐specific, nonreceptor protein tyrosine kinase Lck has been purified from an Escherichia coli expression system using a monoclonal antibody column followed by dye‐affinity chromatography. Polyacrylamide gel electrophoretic analysis of purified protein revealed a single 56 kDa band, indicating that recombinant Lck was purified to near‐homogeneity. The purified enzyme displayed tyrosine kinase activity as measured by both autophosphorylation and phosphorylation of exogenous substrates. Biochemical properties including protein phosphorylation and kinetic characteristics of the enzyme have been assessed. Peptide map analysis revealed that bacterially expressed Lck is phosphorylated predominantly on the autophosphorylation site (tyrosine‐394), which is characteristic for activated protein tyrosine kinases. Indeed, we found that the recombinant enzyme is approximately fivefold more active than Lck from resting T cells, which is extensively phosphorylated at the regulatory carboxy‐terminal tyrosine residue (tyrosine‐505). Thus, we have overproduced recombinant human Lck in E. coli and developed a simple two‐step purification procedure which yields highly active enzyme. This will enable the identification and characterization of potential regulators and targets of Lck and thereby greatly facilitate studies which will clarify its role in T cell signal transduction. © 1994 Wiley‐Liss, Inc.