Biomaterial Database

Human apolipoprotein E. Receptor binding activity of truncated variants with carboxyl-terminal deletions. 1989

A Lalazar, and R W Mahley

Gladstone Foundation Laboratories for Cardiovascular Disease, Department of Pathology, University of California, San Francisco 94140-0608.

The amino-terminal thrombolytic fragment (residues 1-191) of human apolipoprotein (apo) E was previously shown to be fully active in binding to the low density lipoprotein receptor. In this study, truncated apoE variants with progressive deletions at the carboxyl terminus were produced in Escherichia coli by linker-insertion mutagenesis to define the minimum amino-terminal structure necessary for full receptor binding. These truncated forms of apoE, comprising residues 1-166, 1-170, 1-174, or 1-183, were combined with the phospholipid dimyristoylphosphatidylcholine and tested for their ability to bind to low density lipoprotein receptors on human fibroblasts. All of the truncated variants formed typical discoidal particles when combined with the phospholipid, and the particles could be isolated by density gradient ultracentrifugation. The 1-166 and 1-170 variants had very little receptor binding activity (1%), whereas the 1-183 variant had nearly full activity (85%). The 1-174 variant had 19% activity. We conclude that the 171-183 region of apoE is important for receptor binding, either by contributing one or more residues essential for receptor binding or, more likely, by stabilizing or aligning the region known to be crucial for receptor binding, in the vicinity of residues 140-160.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D002872	Chromosome Deletion	Actual loss of portion of a chromosome.	Monosomy, Partial,Partial Monosomy,Deletion, Chromosome,Deletions, Chromosome,Monosomies, Partial,Partial Monosomies
D005796	Genes	A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms.	Cistron,Gene,Genetic Materials,Cistrons,Genetic Material,Material, Genetic,Materials, Genetic
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D001057	Apolipoproteins E	A class of protein components which can be found in several lipoproteins including HIGH-DENSITY LIPOPROTEINS; VERY-LOW-DENSITY LIPOPROTEINS; and CHYLOMICRONS. Synthesized in most organs, Apo E is important in the global transport of lipids and cholesterol throughout the body. Apo E is also a ligand for LDL receptors (RECEPTORS, LDL) that mediates the binding, internalization, and catabolism of lipoprotein particles in cells. There are several allelic isoforms (such as E2, E3, and E4). Deficiency or defects in Apo E are causes of HYPERLIPOPROTEINEMIA TYPE III.	Apo-E,Apo E,Apo E Isoproteins,ApoE,Apolipoprotein E Isoproteins,Apoprotein (E),Apoproteins E,Isoproteins, Apo E,Isoproteins, Apolipoprotein E
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA