Structural and Metabolic Relationships Between Goldfish Brain Glycoproteins Participating in Functional Plasticity of the Central Nervous System

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Abstract
Ependymins β and γ (MW 32,000 and 26,000 daltons) are two secreted goldfish brain glycoproteins that exhibit a specifically enhanced turnover rate when the animals successfully acquire a new pattern of swimming behaviour. Both proteins are bound identically to concanavalin A and can be isolated from brain extracellular fluid and from brain cytoplasm by lectin affinity chromatography. Radioimmunoassay data, using purified 125I- labeled ependymins and antisera directed against ependymin β or ependymin γ, show complete cross-reactivity between the two proteins. It is demonstrated by Scatchardplot analysis that the antisera recognize identical immunological determinants in both proteins. The amino acid composition of the ependymins is similar, and several identical polypeptide fragments are obtained after limited proteolysis with Staphylococcus aureus protease. The proteins are capable of forming complexes of the compositions γ2, βγ, and β2. A protease present in the extracellular fluid of goldfish brain promotes proteolysis of ependymin β to ependymin γ. The finding that ependymin γ is physiologically derived from ependymin β suggests the possibility that ependymin β might exert its biological function during consolidation of new behavioural patterns via smaller polypeptide fragments.