Apolipoprotein B-32: a new truncated mutant of human apolipoprotein B capable of forming particles in the low density lipoprotein range.
We have identified a new species of apolipoprotein (apo) B in an individual with heterozygous hypobetalipoproteinemia. The new apo B (apo B-32) is the result of a single point mutation (1450 Gln----Stop) in the apo B gene that prevents full length translation. Apo B-32 is predicted to contain the 1449 amino-terminal amino acids of apo B-100 and is associated with a markedly decreased low density lipoprotein (LDL) cholesterol level. The density distribution of apo B-32 in the plasma lipoproteins makes it unique amongst other truncated apo B species. Normally, apo B-100 is found in both very low density lipoprotein (VLDL) and LDL particles. However, the majority of the apo B-32 protein was found in the high density lipoprotein (HDL) and lipoprotein-deplete (d greater than 1.21 g/ml) fractions, suggesting that it was mainly assembled into abnormally dense lipoprotein particles. A small amount of apo B-32 was also found in the LDL, making it the shortest known apo B variant capable of forming particles in this density range. Apo B-32 was undetected in VLDL. The apo B-32 mutation further defines the minimum length of the apo B protein that is required for the assembly of LDL.
McCormick
S P
SP
Pathology Department, Christchurch School of Medicine, Christchurch Hospital, New Zealand.
Fellowes
A P
AP
Walmsley
T A
TA
George
P M
PM
D000368:Aged; D000595:Amino Acid Sequence; D001055:Apolipoproteins B / Q000097:blood* / Q000737:chemistry / Q000235:genetics; D001483:Base Sequence; D005260:Female; D006579:Heterozygote; D006801:Humans; D006995:Hypobetalipoproteinemias / Q000097:blood*; D015151:Immunoblotting; D008077:Lipoproteins, LDL / Q000097:blood*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics
D001055:Apolipoproteins B; D008077:Lipoproteins, LDL; C074121:apolipoprotein B-32