1 Max-Planck-Institute for Psychiatry, Department of Neurochemistry, D-82152 Martinsried, Germany
2 CIHR Group in Matrix Dynamics, University of Toronto, Toronto, Ontario M5S 3E2, Canada
3 Institute of Molecular Biology and Medical Chemistry, Otto-von-Guericke-University, D-39120 Magdeburg, Germany
Ependymins are secretory, calcium-binding sialoproteins which are the predominant constituents of the cerebrospinal fluid of many teleost fish. A bound form of these regeneration-responsive glycoproteins is associated with collagen fibrils of the extracellular matrix. Here, the tryptophan fluorescence of ependymins was monitored at various Ca2+ concentrations. Two distinct states were identified with a relatively sharp transition at about 1 mM Ca2+. In agreement with previous circular dichroism measurements, this strongly supports the hypothesis that a calcium-induced conformational change is important for the interaction of ependymins with components of the extracellular matrix. Such interactions with constituents of various basal laminae would also explain the important roles of piscine ependymins as well as invertebrate and mammalian ependymin-related proteins for cell adhesion processes and cell migration.
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