Table 1.

Structural differences among apolipoprotein E (apoE) isoforms.

Isoform	Amino Acids (112, 158)	Structural Description
ApoE2	Cys, Cys	Cys-158 at the N-terminal domain reduces receptor binding. Arg-61 is internal to the helical domain of the N-terminus. Ability to dimerize through cysteine-cysteine bonds, forming homodimers and multimers.
ApoE3	Cys, Arg	Presence of salt bridge between Arg-158 and Asp–154. Arg-61 is internal to the helical domain of the N-terminus. Ability to dimerize through a cysteine-cysteine bond, forming homodimers.
ApoE4	Arg, Arg	Asp-154 interacts with Arg-150, altering the receptor binding region. Ionic interaction between Arg-61 and Glu-255 in the C-terminal domain. No cysteine residue.