A novel apolipoprotein E5 variant with a 24-bp insertion causing hyperlipidemia
We have isolated and analyzed apolipoprotein E5 gene from a patient with hyperlipoproteinemia. Apolipoprotein E5 is a variant of apolipoprotein E with two additional units of positive charge and smaller apparent molecular weight than apolipoprotein E3, which is the major isoform of apolipoprotein E. The heterozygous gene of apolipoprotein E5/3 from the patient was cloned into lambda phage. The cloned apolipoprotein E genes were subcloned into a murine retrovirus shuttle vector and were expressed. One out of four clones expressed apolipoprotein E5. The analysis of the nucleotide sequence of the exons and exon-intron boundary regions has shown a G to A substitution in the 18th nucleotide from the 5'-end of the third exon. This single base substitution changes the amino acid residue Glu to Lys at the third position from the amino-terminus of the mature protein, and gives two additional units of positive charge to the molecule.