Comparative studies on plasma low density lipoproteins from pig and man

1. 1. Low density lipoproteins (LDL) were isolated from pig plasma by ultracentrifugal flotation in KBr between densities 1·020 and 1·060 g/ml (LDL 1 ) and between 1·060 and 1·090 g/ml (LDL 2 ). 2. 2. The chemical, immunological and physical properties of LDL 1 and LDL 2 were compared with each other and with human LDL. 3. 3. LDL 1 and LDL 2 were delipidated and fractionated by chromatography on Sephadex G-150 in 0·1 M Tris-HC1, pH 8·0, containing 2 mM sodium decyl sulfate. ApoLDL 1 and apoLDL 2 were immunochemically identical, had only minor differences of amino acid composition and had indistinguishable circular dichroic spectra. The apoproteins were very similar in amino acid composition and circular dichroic spectra to human apoLDL. 4. 4. Our findings strongly suggest that the apoproteins from pig LDL 1 and LDL 2 are identical and that this protein is similar but not identical to apoLDL from man.