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Journal of Lipid Research, Vol 38, 2111-2124, Copyright © 1997 by Lipid Research, Inc.
Y Andersson, A Lookene, Y Shen, S Nilsson, L Thelander and G Olivecrona
Guinea pig apolipoprotein C-II (apoC-II) lacks four amino acid residues in
the amino-terminal, lipid-binding part compared to apoC-II from other
mammalian species (Andersson et al. 1991. J. Biol. Chem. 266: 4074-4080).
To explore whether this structural difference explains the low ability of
guinea pig plasma to activate lipoprotein lipase in vitro, we have
expressed guinea pig apoC-II in Escherichia coli and have constructed an
insertion mutant with the four missing amino acid residues compared to
human apoC-II. With a synthetic emulsion of long- chain triacylglycerols,
both the wild-type guinea pig apoC-II and the insertion mutant stimulated
lipoprotein lipase similar to human apoC- II, but with chylomicrons from an
apoC-II-deficient patient, 5- to 10- fold more of both wild-type guinea pig
apoC-II and the insertion mutant were needed. Studies of tryptophane
fluorescence indicated a slight difference in how guinea pig apoC-II
interacted with liposomes, and presumably with lipoproteins, as compared to
human apoC-II. The level of apoC-II (11.5 +/- 5.4 microg/ml) was lower in
guinea pig compared to human plasma, and most of guinea pig apoC-II was on
HDL-like particles. These had decreased ability to donate apoC-II to lipid
emulsions compared to human HDL. Some guinea pig apoC-II was associated
with LDL which, as demonstrated by surface plasmon resonance, had higher
affinity for lipoprotein lipase than human LDL, and inhibited rather than
stimulated the lipase reaction in vitro. We conclude that while guinea pig
apoC-II is fully competent to stimulate lipoprotein lipase, the sum of
several different factors explains the low ability of guinea pig plasma to
accomplish stimulation.
ARTICLES
Guinea pig apolipoprotein C-II: expression in E. coli, functional studies of recombinant wild-type and mutated variants, and distribution on plasma lipoproteins
Department of Medical Biochemistry and Biophysics, University of Umea, Sweden.
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