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MODIFICATIONS OF MYELIN BASIC PROTEIN WHICH OCCUR DURING ITS ISOLATION 1, 2
Author(s) -
Chou F. CH.,
Chou CH. J.,
Shapira R.,
Kibler R. F.
Publication year - 1977
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1977.tb10668.x
Subject(s) - deamidation , chemistry , chromatography , elution , myelin basic protein , peptide , chloroform , arginine , acetone , methanol , myelin , biochemistry , enzyme , amino acid , organic chemistry , biology , neuroscience , central nervous system
— Chromatography of myelin basic protein (BP) on carboxymethylcellulose gives a pattern of multiple components, of which three are major. Component 1 is considered the unmodified species of BP while component 2 has been found to be modified primarily by deamidation and component 3 by phosphorylation (C hou et al. , 1976). 3 In contrast to BP prepared from tissue delipidated in the standard fashion in chloroform–methanol (CM powder), BP prepared from tissue delipidated first in acetone and then in chloroform–methanol (ACM powder) gave an elution pattern on carboxymethylcellulose characterized by a decrease in component 1 and an increase in the earlier eluting, less basic components. Studies with radiolabelled component 1 showed that this difference in elution patterns was due to the partial conversion of component 1 to less basic components during the extraction of ACM powder at neutral pH. The components derived from component 1 (D2, D3 and D4) were then isolated and subjected to tryptic peptide map analyses and determination of their carboxy‐terminal arginine content and content of phosphorus. None of the derived components contained phosphorus but tryptic peptide map analyses did show the presence of two minor peptides, T14M 2 and T20M, previously found in component 2 from CM powder and considered to be the deamidation products of their parent peptides T14 and T20 (C hou et al. , 1976). In addition components D3 and D4 were shown to have lost appreciable arginine from their carboxy‐termini. Since none of the efforts to reduce enzyme activity in vitro had any appreciable effect on components 2 and 3 it was concluded that phosphorylation probably occurs exclusively in vivo , that deamidation occurs both in vivo and in vitro and that loss of carboxy‐terminal arginine occurs exclusively in vitro.