title: Identification, characterization, cloning, and expression of apolipoprotein C-IV, a novel sialoglycoprotein of rabbit plasma lipoproteins.
abstract: We have identified and characterized a novel proline- and arginine-rich protein component of lipoproteins, present in up to five sialylated isoforms, in rabbit blood plasma. The pI of the desialylated protein is 5.7. Based upon its N-terminal sequence, a complete cDNA sequence of 555 nucleotides was cloned from rabbit liver. The synthesized protein is predicted to contain 124 amino acids, including a typical signal peptide of 27 residues. The mature protein of 97 amino acids, designated apolipoprotein C-IV, is associated with the lipoproteins of blood plasma, primarily very low density and high density lipoproteins. It contains two potential amphipathic helices characteristic of plasma apolipoproteins and forms discoidal micelles with phosphatidylcholine. Northern analysis shows a single 0.6-kilobase apolipoprotein C-IV mRNA, detected only in the liver, and Southern analysis suggests a single copy gene. Sialylated apolipoprotein C-IV is secreted from transfected mammalian cells. Nucleotide sequence comparisons demonstrate a strong homology to portions of the upstream regions of the mouse and human apolipoprotein C2 genes, within each of which a distinct gene has recently been identified. The nucleotide sequences and the predicted amino acid sequences, as well as corresponding cDNA sequences in the rat and monkey, indicate that the apolipoprotein C4 gene has been highly conserved during mammalian evolution.
authors.affiliation: Cardiovascular Research Institute, University of California, San Francisco 94143-0130, USA.
authors.forename: L H
authors.initials: LH
authors.lastname: Zhang
authors.forename: L
authors.initials: L
authors.lastname: Kotite
authors.forename: R J
authors.initials: RJ
authors.lastname: Havel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001056:Apolipoproteins C / Q000096:biosynthesis* / Q000097:blood / Q000302:isolation & purification; D001120:Arginine; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D015870:Gene Expression; D000882:Haplorhini; D006801:Humans; D007525:Isoelectric Focusing; D008074:Lipoproteins / Q000097:blood / Q000302:isolation & purification; D008099:Liver / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D011392:Proline; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000097:blood / Q000302:isolation & purification
chemical_list: C097349:APOC4 protein, human; C484352:Apoc4 protein, mouse; D001056:Apolipoproteins C; D017931:DNA Primers; D018076:DNA, Complementary; D008074:Lipoproteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012795:Sialoglycoproteins; D001120:Arginine; D011392:Proline