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Dimerization of midkine by tissue transglutaminase and its functional implication
S Kojima1, T Inui, H Muramatsu
1Laboratory of Gene Technology and Safety, Tsukuba Life Science Center, The Institute of Physical and Chemical Research (RIKEN), Koyadai, Tsukuba, Ibaraki 305, Japan. kojima@rtc.riken.go.jp
The Journal of Biological Chemistry
|April 4, 1997
Summary
Tissue transglutaminase cross-linking of Midkine (MK) forms dimers, potentiated by heparin. This dimer formation is crucial for MK
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Midkine (MK) is a growth/differentiation factor induced by retinoic acid.
- MK is a known substrate for tissue transglutaminase (TGase).
- TGase facilitates cross-linking reactions, forming protein multimers.
Purpose of the Study:
- To investigate the role of TGase in MK multimerization.
- To identify the specific sites of TGase-mediated cross-linking in MK.
- To determine the impact of TGase-induced modifications on MK's biological activity.
Main Methods:
- Incubation of MK with TGase in the presence and absence of heparin.
- Analysis of MK multimer formation using gel filtration chromatography.
- Identification of cross-linking sites via putrescine incorporation and peptide inhibition assays.
- Assessment of MK's effect on plasminogen activator activity in endothelial cells.
Main Results:
- Heparin significantly enhanced MK multimer formation.
- TGase induced dimerization of both the N- and C-terminal half-domains of MK.
- Glutamine residues (Gln42/Gln44 and Gln95) were identified as amine acceptors in the cross-linking.
- A specific peptide (Ala41-Pro51) inhibited cross-linking and abolished MK's biological activity.
- Inhibition was observed for MK monomers but not dimers.
Conclusions:
- TGase-mediated cross-linking leads to MK dimer formation.
- Dimerization, particularly involving specific glutamine residues, is essential for MK's biological function.
- Heparin influences the rate of MK multimerization.
- These findings highlight the significance of post-translational modifications in regulating MK activity.