Molecular cloning and expression of partial cDNAs and deduced amino acid sequence of a carboxyl-terminal fragment of human apolipoprotein B-100

C. F. Wei, S. H. Chen, C. Y. Yang, Y. L. Marcel, R. W. Milne, W. H. Li, J. T. Sparrow, Antonio Gotto, L. Chan

Research output: Contribution to journalArticle

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Abstract

Apolipoprotein (apo) B-100 cDNAs were identified in a human liver cDNA library cloned in the expression vector λgt11. The β-galactosidase-apoB-100 fusion protein was detected by two independently produced low density lipoprotein polyclonal antisera and by three apoB-100 monoclonal antibodies that crossreact with apoB-74. It was not recognized by two apoB-100 monoclonal antibodies that crossreact with apoB-26. The longest clone, λB8, was completely sequenced. It contains a 2.8-kilobase DNA fragment containing the codons for the carboxyl-terminal 836 amino acid residues of apoB-100, as well as the 3' untranslated region of apoB-100 mRNA. We have thus mapped apoB-74 to the carboxyl-terminal portion of apoB-100. The deduced amino acid sequence of the cloned DNA matches the sequences of 14 apoB-100 peptides determined in our laboratory. Minor differences in amino acid sequence were noted in three of the peptides, suggesting polymorphism of apoB-100 at the protein and DNA levels. Secondary structure predictions reveal an unusual pattern for apolipoproteins, consisting of β-structure (24%), α-helical content (33%), and random structure (30%). Ten amphipathic helical regions of 10-24 residues were identified. This carboxyl-terminal fragment of apoB-100 is considerably more hydrophobic than other apolipoproteins with known structure. Its lipid binding regions might include stretches of highly hydrophobic β-sheets as well as amphipathic helices. Our findings on apoB structure might be important for understanding the role of apoB-100-containing lipoproteins in atherosclerosis.

Original languageEnglish (US)
Pages (from-to)7265-7269
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume82
Issue number21
DOIs
StatePublished - 1985

ASJC Scopus subject areas

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