Protein heterogeneity of lipoprotein particles containing apolipoprotein A-I without apolipoprotein A-II and apolipoprotein A-I with apolipoprotein A-II isolated from human plasma.

The protein heterogeneity of fractions isolated by immunoanity chromatography on anti-apolipoprotein A-I and anti-apolipoprotein A-I1 affinity columns was analyzed by high resolution two-dimensional gel electrophoresis. The two-dimen- sional gel electrophoresis profiles of the fractions were analyzed and automatically compared by the computer system MELANIE. Fractions containing apolipoproteins A-I + A-I1 and only A-I as the major protein components have been isolated from plasma and from high density lipoproteins prepared by ultracen- trifugation. Similarities between the profiles of the fractions, as indicated by two-dimensional gel electrophoresis, suggested that those derived from plasma were equivalent to those from high density lipoproteins (HDL), which are particulate in nature. The established apolipoproteins (A-I, A-11, A-IV, C, D, and E) were visible and enriched in fractions from both plasma and HDL. However, plasma-derived fractions showed a much greater degree of protein heterogeneity due largely to enrich- ment in bands corresponding to six additional proteins. They were present in trace amounts in fractions isolated from HDL and certain of the proteins were visible in two-dimensional gel electrophoresis profiles of the plasma. These proteins are con- sidered to be specifically associated with the immunoaffinity- isolated particles. They have been characterized in terms of M, and PI. Computer-assisted measurements of protein spot- staining intensities suggest an asymmetric distribution of the proteins (as well as the established apolipoproteins), with four showing greater prominence in particles containing apolipopro- tein A-I but no apolipoprotein A-11. -James, R.W., D. Hoch- strasser, J-D. Tissot, M. Funk, R. Appel, F. Barja, C. Pel- legrini, A.F. Muller, and D. Pometta. Protein heterogeneity of lipoprotein particles containing apolipoprotein A-I without apolipoprotein A-I1 and apolipoprotein A-I with apolipoprotein A-I1 isolated from human plasma. J. Lipid Res. 1988. 29: 1557- 1571.