Solubilization of proteins in dimethyl sulfoxide by permethylation: Application to structural studies of apolipoprotein B

✍ Scribed by Matti Vauhkonen; Paavo K.J. Kinnunen; Heikki Rauvala

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 998 KB
• Volume: 148
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(85)90240-4

✦ Synopsis

The delipidated protein moiety. apolipoprotein B, of human low-density lipoproteins was permethylated in potassium butoxide/dimethyl sulfoxide with methyl iodide. The derivatized protein was soluble in dimethyl sulfoxide and, in the presence of sodium dodecyl sulfate, in an aqueous buffer. Analysis of the methylated apolipoprotein B by polyacrylamide gradient gel electrophoresis in the presence of sodium dodecyl sulfate revealed five discrete bands of lower molecular mass than that of the parent 265-kDa protein, which disappeared upon permethylation. The electrophoretic behavior of the methylated apolipoprotein B was distinctly different from that of the other methylated proteins studied, including transferrin, bovine serum albumin, aldolase, B-lactoglobulin, and apohpoprotein A-I, all of which had a higher apparent molecular weight after permethylation as compared to the corresponding native polypeptide. Calculated on the basis of methylated standard proteins the five polypeptides of apolipoprotein B have apparent molecular masses of 9.0, 16.6, 25.6, 35.7, and 46.7 kDa. The results suggest that the protein moiety of human low-density lipoprotein consists of subunits. In general, the results indicate that the permethylation method can be used to solubilize hydrophobic proteins in organic SOlVentS for structural studies.