PRIMARY STRUCTURE OF BEIJING DUCK APOLIPOPROTEIN A-1

The primary structure of Beijing duck apolipoprotein A-1 was determine d by sequencing peptide fragments derived from tryptic and endoprotein ase Asp-N digestion of the protein, and alignment with homologous chic ken apo A-1. All of the peptide fragments were isolated by high-pressu re liquid chromatography (HPLC) with a Vydac C18 column using a triflu oroacetic acid (TFA) buffer system. The N-terminus of the protein was determined to be aspartic acid by directly sequencing 52 residues of t he intact protein. The C-terminus was alanine. The protein contains 24 0 amino acid residues. By analysis of the whole protein and its trypti c peptides, a six amino acid (Arg-Tyr-Phe-Trp-Gln-His) prosegment was determined. No cross-reactivity between duck and human apo A-1 with a goat antiserum against human apo A-1 was found. Sequence analysis of a po A-1 of other species indicates that amino acid substitutions in rat are more extensive than in other mammals. Isoleucine residues in apo A-1 are inversely correlated to the homology of human to other species , except dog.