Probing of the porcine serum lipoprotein surfaces by Mn(II) binding: an e.s.r. study |
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Authors: | Janko N Herak Greta Pifat Jasminka Brnjas-Kraljevi? Gabriele Knipping Anton Holasek |
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Institution: | 1. Faculty of Pharmacy and Biochemistry, University of Zagreb, 4100 Zagreb, Croatia, Yugoslavia;2. Rudjer Boskovi? Institute, University of Zagreb, 4100 Zagreb, Croatia, Yugoslavia;3. Faculty of Medicine, University of Zagreb, 4100 Zagreb, Croatia, Yugoslavia;4. Institute of Medical Biochemistry, University of Graz, 8010 Graz, Austria |
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Abstract: | Mn(II) ions were used for probing the surfaces of porcine LDL1, LDL2 and HDL. From the intensity of the e.p.r. lines corresponding to the unbound Mn(II) the percentage of the ions bound to the lipoprotein surface is determined. From the titration curves the binding parameters, dissociation constant. Kd, and the number of binding sites, n, in all the three lipoproteins studied have been derived. There are at least two types of binding sites in each lipoprotein class. The ”weak’ binding sites are charaterized by approximately the same value of and different values for n (n = 114 for LDL1, n = 135 for LDL2 and n = 28 for HDL). Similarly, for the ”strong’ binding sites Kd ≈ 1.6 × 10?4 mol l?1 and the number of binding sites is 15, 20 and 5 for LDL1, LDL2 and HDL respectively. It is concluded that the binding sites are probably located in the protein part of the lipoproteins and that they are mainly associated with the negatively charged amino acids. |
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Keywords: | Proteins low density lipprotein high density lipoprotein Mn(II) binding e s r |
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