The complete amino acid sequence of chicken plasma apolipoprotein(apo)A-I wasdetermined by sequencing overlapping peptide fragments produced by trypsin,S.aureus V8 protease,and cyanogen bromide cleavage respectively.All of the peptide fragments were purified on a Watersor on a Beckman HPLC system with a Vydae C_(18) column using 0.1% TFA in water as buffer A,and0.08% TFA in 95% acetomtrile and 5% water as buffer B.Most of the peaks separated by thesesystems were pure.The partially purified fractions were subjected to rechromatography with aHypersil ODS column using 0.005M sodium phosphate,pH 6.0,as buffer A,and 90% acetonitrileand 10% water as buffer B.The N-terminus of chicken apo A-I was determined to be aspartic acidby directly sequencing the intact protein up to 30 residues,while the C-terminus was identified asalanine by carboxypeptidase Y cleavage.There are 240 amino acid residues in mature chicken apoA-I.By direct analysis of cyanogen bromide peptide,we also determined the sequence of a 6 aminoacid prosegment,which is present at approximately 10% of the molar amount of the mature proteinin chicken plasma.