Journal of Lipid Research, Vol 21, 913-920, Copyright © 1980 by Lipid Research, Inc.
Microcomplement fixation and particle size of chicken lipoproteins
LA Hillyard, HM White and S Abraham
Conformational changes of the lipoproteins of chicken serum and egg yolk
were studied with the use of microcomplement fixation. Egg yolk very low
density lipoproteins and serum total low density lipoproteins were
separated by 2% agarose gel chromatography into four and five fractions,
respectively, with different average particle diameters. A correlation
between percent complement fixed at equivalence and particle diameter was
noted. Thus, smaller particles fixed less complement. The shortening of the
radius of curvature could alter the steric fit of apolipoprotein with
antibody and, as a consequence, reduce complement fixation. The patterns
obtained after delipidation of very low density lipoproteins indicate a
general distortion of apolipoprotein conformation supporting the view that
lipids are essential for maintaining the conformation of these
apolipoproteins. On the other hand, the general conformation of the high
density apolipoproteins does not appear to depend on lipid content. It has
been reported that lipids restrain the free movement of these
apolipoproteins. After delipidation, the greater degree of freedom allowed
the apolipoprotein may increase the strength of the antigen- antibody union
and therefore an increase in complement fixation is observed. These studies
demonstrate the applicability of quantitative microcomplement fixation to
the eludication of lipoprotein structure and function.
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