Ionization Behaviour of Native Apolipoproteins and of Their Complexes with Lecithin
Frederik SOETEWEYa b, Marie‐José LIEVENSa b, Raphaël VERCAEMSTa b, Maryvonne Rosseneua b, Hubert Peetersa b, Virgil Brownc
- aSimon Stevin Instituut voor Wetenschappelijk Onderzoek, Akademisch Ziekenhuis St-Jan, Ruddershove, B-8000 Brugge, Belgium
- bSimon Stevin Instituut voor Wetenschappelijk Onderzoek, Akademisch Ziekenhuis St‐Jan, Ruddershove, B‐8000 Brugge, Belgium
- cDepartment of Biochemistry and Biophysics, University of California, San Diego, P.O. Box 109, La Jolla, California, U.S.A. 92037
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Abstract
A comparison of the ionization behaviour of the human apoA-II, apoC-I, apoC-III proteins and of their complexes with dimyristoyl lecithin is based on potentiometric titration of the basic and acidic residues and spectrophotometric titration of the phenolic groups. Experimental data suggest that a number of lysine, arginine, aspartic acid and glutamic acid residues are masked in the complexes. For each of these amino acids and in all three proteins the number of masked residues is consistent with the content of those regions predicted to be involved in lipid binding by the model of Segrest et al. [FEBS Lett. 38, 247-253 (1974)]. These data taken together with the results of calorimetric and titration experiments with the apoA-I protein reported in the accompanying article [Rosseneu et al. (1977) Eur. J. Biochem. 79, 251-257] strongly support the general nature of the proposed model and further suggest that ionic interactions have some role in the formation of the dimyristoyl lecithin/apolipoprotein complexes.
TL;DRA tentative localisation of lysine, arginine, aspartic acid and glutamic acid residues directly involved in phospholipid binding is suggested, assuming that such helical regions are involved in apoprotein-phospholipids association. (Semantic Scholar)