STUDIES ON THE ACID‐EXTRACTABLE PROTEINS OF BOVINE BRAIN WHITE MATTER *

MANY investigators have studied the nature of brain proteins which are extracted with aqueous solvents in the region of neutral pH, but relatively few have investigated brain proteins extracted with dilute aqueous acid. The latter studies have been limited almost exclusively to basic proteins capable of inducing experimental allergic encephalomyelitis (EAE) and have resulted in the isolation of reasonably pure basic proteins (or polypeptides) having high EAE-inducing activity (EINSTEIN, ROBERTSON, DICAPRIO and MOORE, 1962; KIBLER, Fox and SHAPIRA, 1964; b s , 1965~; WOLFGRAM, 1965; CASPARY and FIELD, 1965; NAKAQ and ROBOZ-EINSTEIN, 1965). In work reported by HONEGGER (1965) the nature of the relatively acidic proteins extracted by dilute aqueous acid was investigated to a limited extent by means of gel filtration and starch gel electrophoresis. The present studies were undertaken to examine the constituents of a ‘viscous protein’ fraction iirst prepared by LEBARON and ROTHLEDER (1960). According to the method used by these authors for preparing phosphoinositide-protein complexes (phosphatidopeptides) from bovine brain white matter, the tissue was first depleted of a considerable amount of its protein and most of its lipid by successive treatments with CHC1,: CH,OH (2: 1, v/v), H,O, and 0.03 N-HCI. The HC1 extract, which appeared rather viscous, was accordingly designated by LEBARON and ROTHLEDER as the ‘viscous protein’ fraction. Attempts to fractionate the acid-extractable proteins comprising the ‘viscous protein’ fraction of bovine white matter led to a method whereby a glycine-rich basic protein can be readily obtained both in reasonable purity and high yield. This basic protein is highly active in inducing EAE in guinea pigs (KIES, ALVORD, MARTENSON and LEBARON, 1966). In addition, the procedure permits the preparation of a fraction of large molecular-size proteins rich in glutamic and aspartic acids. An abstract of this work has appeared elsewhere (MARTENSON and LEBARON, 1965).