Effect of metallic cations and pH on reassembly of glial fibrillary acidic protein.
Glial fibrillary acidic protein (GFAP), which was purified from acetone powder of the bovine spinal cord, was reassembled in 0.1 M imidazole HCl buffer containing metallic cations, Ca(2+), Mg(2+), Na(+) or K(+) at physiological or more acidic pH. An electron microscopy revealed reassembled glial filaments at pH 6.8 without any cations but amorphous aggregates at pH 6.3 which were readily observed as a white precipitate by the naked eye. Under more alkaline pH (pH 7.4) only rod-shaped short filaments were formed. In the presence of mM concentrations of Ca(2+) or Mg(2+), thick bundles of glial filaments, detectable by light microscopy, were formed at acidic pH. At pH 7.4 long reassembled filaments could be formed in the buffer containing divalent cations. Na(+) (0.1 M) made filament-like structures of GFAP but they are rather random compared to the filaments promoted by the divalent cations. K(+) made only amorphous aggregation of the short filaments. These findings indicate that the reassembly of GFAP at physiological pH requires essentially divalent cations but not ionic strength.
Tanaka
J
J
Department of Neuropsychiatry, Osaka University Medical School, 1-1-50, Fukushima, Fukushima-ku, Osaka 553, Japan.
Tada
K
K
Takeda
M
M
Hariguchi
S
S
Nishimura
T
T