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Minibrain kinase/dual‐specificity tyrosine phosphorylation‐regulated kinase 1A (Mnb/Dyrk1A) does not require tyrosine phosphorylation for activity in vitro
Author(s) -
Hwang YuWen,
ChenHwang MoChou,
Murakami Noriko,
Adayev Tatyana,
Lee Eric,
Bolton David
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a986
Subject(s) - dyrk1a , phosphorylation , autophosphorylation , tyrosine , tyrosine phosphorylation , protein tyrosine phosphatase , biochemistry , microbiology and biotechnology , kinase , biology , tyrosine kinase , chemistry , protein kinase a , signal transduction
The Mnb/Dyrk1A gene is localized in human chromosome 21 and its aberrant expression is associated with the learning and memory deficits of Down syndrome. Mnb/Dyrk1A contains an Y 319 XY 321 motif shared by all members of the Mnb/Dyrk1A protein kinase family. Tyrosine residues in the YXY motif are phosphorylated in Mnb/Dyrk1A prepared from Escherichia coli and from eukaryotic cells. It has been proposed that phosphorylation of the YXY motif is required for kinase activation, a mechanism similar to the activation of mitogen activated protein through phosphorylation of the TXY motif. In this study, the role of tyrosine phosphorylation in the activity of Mnb/Dyrk1A was investigated in detail. Wild‐type Mnb/Dyrk1A with a reduced level of PY was prepared by treating Escherichia coli ‐produced Mnb/Dyrk1A with two different protein tyrosine phosphatases. The resulting PY‐depleted Mnb/Dyrk1A could not regain PY during autophosphorylation but was as active as the untreated control. These findings were further supported by the observation that Mnb/Dyrk1A retained measurable enzymatic activity when both tyrosine residues in the YXY motif were replaced with either histidine or glutamine residues. Together, we conclude that tyrosine phosphorylation as well as tyrosine residues in the YXY motif are not directly involved in Mnb/Dyrk1A enzymatic activity.