Human plasma proapoA-I: isolation and amino-terminal sequence.
Human apoA-I is synthesized as preproapoA-I, a 267 amino acid precursor apolipoprotein. PreproapoA-I initially undergoes intracellular co-translational proteolytic cleavage into proapoA-I. ProapoA-I is secreted from the cell and was isolated from thoracic duct lymph in the apoA-I1 isoform position. The amino-terminal sequence of proapoA-I isolated from human lymph revealed the presence of 6 additional amino acids, Arg-His-Phe-Trp-Gln-Gln, on the amino-terminal end of apoA-I consistent with the proapoA-I sequence determined by nucleic acid sequence analysis of cloned apoA-I. Our results indicate that proapoA-I is present in human plasma, and undergoes post-translational proteolytic cleavage to mature plasma apoA-I.
D000595:Amino Acid Sequence; D016632:Apolipoprotein A-I; D001053:Apolipoproteins / Q000097:blood*; D055598:Chemical Phenomena; D002621:Chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D011498:Protein Precursors / Q000097:blood*
D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D011498:Protein Precursors