ABSTRACT
Apo A-I of Beijing duck was first cleavaged by CNBr into 11 peptide fragments which were further separated and purified by preparative SDS-PAGE and HPLC, then their molecular weights and N-terminal amino acid sequences were also determined. According to the molecular weights and N-terminal amino acid sequences of each fragment the positions of peptide fragments 3-10 in apo A-I molecule were localized at the sites of amino acid sequences 64-240, 74-240, 64-206, 1-163, 1-36, 171-206, 207-240 and 137-170 respectively. The studied results of their main functions are as following: (1) All the fragments could combine with lipids to form lipsomes of various sizes. The fragment Longer, the size will be larger. (2) The ability of the fragments 3-10 to activate LCAT equals to 65%, 52%, 60%, 39%, 8%, 7%, 0% and 2% of that of the whole apo A-I molecule respectively, showing that the activating sequence is localized in amino acid residues 64-136. (3) Only the liposomes formed with fragments 3, 4 and 9 could combine with the HDL receptor of liver cell membrane of Beijing duck; the rest of the liposomes demonstrated essentially no binding ability. As peptide fragments 3 and 4 also contained fragment 9, the result indicated that amino acids 207-240 maybe the fragment that combined with HDL receptor.
