Journal of Lipid Research, Vol 18, 69-76, Copyright © 1977 by Lipid Research, Inc.
Analysis of rat serum apolipoproteins by isoelectric focusing. II. Studies on the low molecular weight subunits
JB Swaney and LI Gidez
The low molecular weight proteins of rat apo HDL and apo VLDL have been
isolated and analyzed by the technique of isoelectric focusing. Sephadex
fractions from apo HDL (HS-3) and apo VLDL (VS-3) that contain these
proteins reveal three major bands with apparent isoelectric points of pH
4.50, 4.67, and 4.74, as well as three minor bands at pH 4.43, 4.57, and
4.61. In addition, apo HDL has a major band at pI of 4.83. DEAE-Cellulose
chromatography was used to prepare purified fractions of these components
that were characterized by N-terminal analyses and molecular weight
determinantions by SDS gel electrophoresis. The major low molecular weight
components of apo HDL were focused on a slab gel and the bands were
identified as A-II (pI 4.83), C-II (pI 4.74), C-III-0 (pI 4.67), and
C-III-3 (pI 4.50). Neuraminidase treatment of apo HDL, followed by
isoelectric focusing, suggested that the other bands, which have not
previously been reported, may be additional forms of the C-III protein,
differing only in their content of sialic acid.