title: The proline-rich region of 18.5 kDa myelin basic protein binds to the SH3-domain of Fyn tyrosine kinase with the aid of an upstream segment to form a dynamic complex in vitro.
abstract: The intrinsically disordered 18.5 kDa classic isoform of MBP (myelin basic protein) interacts with Fyn kinase during oligodendrocyte development and myelination. It does so primarily via a central proline-rich SH3 (Src homology 3) ligand (T92-R104, murine 18.5 kDa MBP sequence numbering) that is part of a molecular switch due to its high degree of conservation and modification by MAP (mitogen-activated protein) and other kinases, especially at residues T92 and T95. Here, we show using co-transfection experiments of an early developmental oligodendroglial cell line (N19) that an MBP segment upstream of the primary ligand is involved in MBP-Fyn-SH3 association in cellula. Using solution NMR spectroscopy in vitro, we define this segment to comprise MBP residues (T62-L68), and demonstrate further that residues (V83-P93) are the predominant SH3-target, assessed by the degree of chemical shift change upon titration. We show by chemical shift index analysis that there is no formation of local poly-proline type II structure in the proline-rich segment upon binding, and by NOE (nuclear Overhauser effect) and relaxation measurements that MBP remains dynamic even while complexed with Fyn-SH3. The association is a new example first of a non-canonical SH3-domain interaction and second of a fuzzy MBP complex.
authors.affiliation: *Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Miguel
authors.initials: M
authors.lastname: De Avila
authors.affiliation: *Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Kenrick A
authors.initials: KA
authors.lastname: Vassall
authors.affiliation: *Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Graham S T
authors.initials: GS
authors.lastname: Smith
authors.affiliation: *Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Bamm
authors.affiliation: *Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
authors.forename: George
authors.initials: G
authors.lastname: Harauz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002645:Chickens; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D051379:Mice; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D004676:Myelin Basic Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011392:Proline / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D051076:Proto-Oncogene Proteins c-fyn / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D008024:Ligands; D004676:Myelin Basic Protein; D010455:Peptides; C011083:polyproline; D011392:Proline; D051076:Proto-Oncogene Proteins c-fyn