Journal of Lipid Research, Vol 25, 378-382, Copyright © 1984 by Lipid Research, Inc.
Genetic polymorphism of apolipoprotein E: a variant form of apolipoprotein E2 distinguished by sodium dodecyl sulfate-- polyacrylamide gel electrophoresis
G Utermann, KH Weisgraber, W Weber and RW Mahley
The apolipoprotein E2 ( apoE2 ) variant that possesses a cysteine
substituted for an arginine at residue 158 in the amino acid sequence E2(
Arg158 ----Cys) can be distinguished by sodium dodecyl sulfate-
polyacrylamide gel electrophoresis from other forms of apoE, including E3
(the parent form), E4( Cys112 ----Arg), E2( Arg145 ----Cys), and E2( Lys146
----Gln). The E2( Arg158 ----Cys) migrates as a distinctly separable band
with a higher apparent molecular weight than the other forms. Chemical
modification of apoE2 ( Arg158 ----Cys) with sulfhydryl reagents
(2-bromoethyl)-trimethylammonium bromide or cysteamine, which convert
cysteine to arginyl or lysyl analogues, respectively, abolishes the
difference in apparent molecular weight and results in the co-
electrophoresis of E2( Arg158 ----Cys) with other apoE forms. The
mobilities of the other apoE variants are not affected by these
modifications. These results suggest that the substitution site at residue
158 is a key location, important in modifying the behavior of apoE and in
modulating its apparent molecular weight on sodium dodecyl
sulfate-polyacrylamide gels. Furthermore, the technique used in this study
may be very helpful in distinguishing specific mutant forms of apoE2 .