Ox peripheral nerve myelin membrane. Purification and partial characterization of two basic proteins

Abstract

Two basic proteins were purified from the peripheral nervous system. The isolation was achieved by (1) delipidation with chloroform-butanol mixtures, dry acetone, and dry ether, (2) acid extraction at pH 2 and then (3) dialysis against distilled water, lyophilization, and solubilization in pH-10.7 buffer. Further purification steps included: (4) ion exchange chromatography on QAE-Sephadex G-25 and (5) gel filtration on Sephadex G-75. Each of the two basic proteins was shown to be homogeneous by disc electrophoresis at pH 2.0, 4.3, and 9.2. The acid extractable proteins of an isolated fraction from peripheral nerve were studied by using gel filtration and disc electrophoresis techniques. Two basic proteins were also recovered in this case. These proteins gave the same elution volumes and the same electrophoretic mobility as the basic proteins recovered from peripheral nerve. Myelin was extracted with butanol and 72–86 % of the myelin proteins were recovered as soluble lipoproteins. They were compared to the acid extractable proteins. Some properties of the proteins purified from peripheral nerve were determined. (1) Molecular weights of the two basic proteins were estimated by gel filtration and disc electrophoresis. The main basic protein was found to have a molecular weight of 14 200 ± 600. (2) The amino acid composition of the two basic proteins were similar to each other but different from the amino acid composition reported of the basic proteins from central nervous system studied by Dawson 14. No free N-terminal amino acids were detected in either of the two basic proteins.