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Physical properties of bovine white matter proteolipid apoprotein–sodium dodecyl sulfate complexes
Author(s) -
Sakura J. David
Publication year - 1981
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.490060602
Subject(s) - sodium dodecyl sulfate , chemistry , ionic strength , circular dichroism , gel electrophoresis , micelle , polyacrylamide gel electrophoresis , proteolipid protein 1 , chromatography , aqueous solution , biochemistry , organic chemistry , biology , myelin basic protein , myelin , enzyme , neuroscience , central nervous system
Abstract The interaction of bovine white matter proteolipid apoproteins with sodium dodecyl sulfate (SDS) was studied. Equilibrium dialysis binding measurements show that the apoprotein binds approximately 1.5 gm SDS per gram protein at high ionic strength (T/2 =0.17). At low ionic strength (T/2 = 0.01) the protein binds only 0.90 gm per gram protein. The Stokes radius of the proteolipid protein is 40 Å. Based on the circular dichroism spectrum, the apoprotein contains less than 20% α‐helix structure in either aqueous or 0.1% sodium dodecyl sulfate solution. Analytical SDS‐PAGE (polyacrylamide gel electrophoresis) revealed two polypeptides. The major proteolipid protein migrated with an apparent molecular weight of 26,000 daltons. The minor proteolipid protein exhibited a molecular weight of 22,200 daltons. The apoprotein showed a marked tendency to aggregate on 8 M urea‐SDS‐polyacrylamide gels or when heated at 100° in excess detergent. These results suggest that the proteolipid proteins have hydrophobic regions that are not embedded within the detergent micelle but are exposed to the solvent. These regions may serve as sites for intermolecular aggregation.