Structural properties of the glial fibrillary acidic protein. Evidence for intermolecular disulfide bonds

Glial fibrillary acidic protein was purified from 4 M urea extracts of bovine brain by DEAE Bio-Gel A chromatography, 30% ammonium sulfate precipitation and hydroxylapatite chromatography. Subunits of about 54 000 daltons are present in solution as polydisperse distributions of polymers largely constrained by the presence of interchain disulfide linkages. Circular dichroism measurements indicate a native conformation containing some alpha-helical structure. The relevance of these findings to the cytoskeletal function of intermediate (80-100 A) filaments is discussed.