1mkn | pdb_00001mkn
N-TERMINAL HALF OF MIDKINE
Structural highlights
FunctionMK_HUMAN Developmentally regulated, secreted growth factor homologous to pleiotrophin (PTN), which has heparin binding activity. Binds anaplastic lymphoma kinase (ALK) which induces ALK activation and subsequent phosphorylation of the insulin receptor substrate (IRS1), followed by the activation of mitogen-activated protein kinase (MAPK) and PI3-kinase, and the induction of cell proliferation. Involved in neointima formation after arterial injury, possibly by mediating leukocyte recruitment. Also involved in early fetal adrenal gland development (By similarity).[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedMidkine (MK) is a 13 kDa heparin-binding polypeptide which enhances neurite outgrowth, neuronal cell survival and plasminogen activator activity. MK is structurally divided into two domains, and most of the biological activities are located on the C-terminal domain. The solution structures of the two domains were determined by NMR. Both domains consist of three antiparallel beta-strands, but the C-terminal domain has a long flexible hairpin loop where a heparin-binding consensus sequence is located. Basic residues on the beta-sheet of the C-terminal domain form another heparin-binding site. Measurement of NMR signals in the presence of a heparin oligosaccharides verified that multiple amino acids in the two sites participated in heparin binding. The MK dimer has been shown to be the active form, giving signals to endothelial cells and probably to neuronal cells. We present a head-to-head dimer model of MK. The model was supported by the results of cross-linking experiments using transglutaminase. The dimer has a fused heparin-binding site at the dimer interface of the C-terminal domain, and the heparin-binding sites on MK fit the sulfate group clusters on heparin. These features are consistent with the proposed stronger heparin-binding activity and biological activity of the dimer. Solution structure of midkine, a new heparin-binding growth factor.,Iwasaki W, Nagata K, Hatanaka H, Inui T, Kimura T, Muramatsu T, Yoshida K, Tasumi M, Inagaki F EMBO J. 1997 Dec 1;16(23):6936-46. PMID:9384573[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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