Apolipoprotein B-100 (APOB)
The protein contains 4563 amino acids for an estimated molecular weight of 515605 Da.
Apolipoprotein B is a major protein constituent of chylomicrons (apo B-48), LDL (apo B-100) and VLDL (apo B-100). Apo B-100 functions as a recognition signal for the cellular binding and internalization of LDL particles by the apoB/E receptor. (updated: April 1, 2015)
Protein identification was indicated in the following studies:
- Goodman and co-workers. (2013) The proteomics and interactomics of human erythrocytes. Exp Biol Med (Maywood) 238(5), 509-518.
- Hegedűs and co-workers. (2015) Inconsistencies in the red blood cell membrane proteome analysis: generation of a database for research and diagnostic applications. Database (Oxford) 1-8.
- Bryk and co-workers. (2017) Quantitative Analysis of Human Red Blood Cell Proteome. J Proteome Res. 16(8), 2752-2761.
- D'Alessandro and co-workers. (2017) Red blood cell proteomics update: is there more to discover? Blood Transfus. 15(2), 182-187.
Methods
The following articles were analysed to gather the proteome content of erythrocytes.
The gene or protein list provided in the studies were processed using the ID mapping API of Uniprot in September 2018. The number of proteins identified and mapped without ambiguity in these studies is indicated below.
Only Swiss-Prot entries (reviewed) were considered for protein evidence assignation.
| Publication | Identification 1 | Uniprot mapping 2 | Not mapped / Obsolete | TrEMBL | Swiss-Prot |
|---|---|---|---|---|---|
| Goodman (2013) | 2289 (gene list) | 2278 | 53 | 20599 | 2269 |
| Lange (2014) | 1234 | 1234 | 7 | 28 | 1224 |
| Hegedus (2015) | 2638 | 2622 | 0 | 235 | 2387 |
| Wilson (2016) | 1658 | 1528 | 170 | 291 | 1068 |
| d'Alessandro (2017) | 1826 | 1817 | 2 | 0 | 1815 |
| Bryk (2017) | 2090 | 2060 | 10 | 108 | 1942 |
| Chu (2018) | 1853 | 1804 | 55 | 362 | 1387 |
1 as available in the article and/or in supplementary material
2 uniprot mapping returns all protein isoforms as one entry
The compilation of older studies can be retrieved from the Red Blood Cell Collection database.
The data and differentiation stages presented below come from the proteomic study and analysis performed by our partners of the GReX consortium, more details are available in their published work.
This protein is annotated as membranous in Gene Ontology.
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Biological Process
Artery morphogenesis
Blood coagulation
Cellular protein metabolic process
Cellular response to prostaglandin stimulus
Cellular response to tumor necrosis factor
Cholesterol efflux
Cholesterol homeostasis
Cholesterol metabolic process
Cholesterol transport
Chylomicron assembly
Chylomicron remnant clearance
Chylomicron remodeling
Fertilization
Flagellated sperm motility
In utero embryonic development
Leukocyte migration
Lipoprotein biosynthetic process
Lipoprotein catabolic process
Lipoprotein metabolic process
Lipoprotein transport
Low-density lipoprotein particle clearance
Low-density lipoprotein particle remodeling
Membrane organization
Nervous system development
Phototransduction, visible light
Positive regulation of cholesterol storage
Positive regulation of gene expression
Positive regulation of lipid storage
Positive regulation of macrophage derived foam cell differentiation
Post-embryonic development
Post-translational protein modification
Receptor-mediated endocytosis
Regulation of cholesterol biosynthetic process
Response to carbohydrate
Response to estradiol
Response to lipopolysaccharide
Response to selenium ion
Response to virus
Retinoid metabolic process
Small molecule metabolic process
Spermatogenesis
Toll-like receptor signaling pathway
Transmembrane transport
Triglyceride catabolic process
Triglyceride mobilization
Very-low-density lipoprotein particle assembly
Very-low-density lipoprotein particle clearance
Cellular Component
Actin cytoskeleton
Chylomicron
Chylomicron remnant
Clathrin-coated endocytic vesicle membrane
Cytoplasm
Cytosol
Early endosome
Endocytic vesicle lumen
Endoplasmic reticulum exit site
Endoplasmic reticulum lumen
Endoplasmic reticulum membrane
Endosome lumen
Endosome membrane
Extracellular exosome
Extracellular region
Extracellular space
Golgi apparatus
High-density lipoprotein particle
Intermediate-density lipoprotein particle
Intracellular membrane-bounded organelle
Lipid droplet
Low-density lipoprotein particle
Lysosomal lumen
Mature chylomicron
Neuronal cell body
Plasma membrane
Smooth endoplasmic reticulum
Very-low-density lipoprotein particle
Vesicle lumen
The reference OMIM entry for this protein is 107730
Apolipoprotein b; apob apob100, included
Apob48, included
Apolipoprotein b allotypes, included
Ag lipoprotein types, included
Low density lipoprotein cholesterol level quantitative trait locus 4, included; ldlcq4, included
DESCRIPTION
Apolipoprotein B is the main apolipoprotein on chylomicrons and low density lipoproteins (LDLs). It occurs in the plasma in 2 main forms, apoB48 and apoB100. The first is synthesized exclusively by the intestine, the second by the liver (summary by Law et al., 1985).CLONING
Lusis et al. (1985) identified cDNA clones for rat liver apoB. Law et al. (1985) cloned human APOB. Deeb et al. (1986) found that APOB RNA isolated from monkey small intestine contained sequences homologous to the cDNA of apolipoprotein B100. These results were interpreted as indicating that intestinal (B48) and hepatic (B100) forms of apoB are coded by a single gene. Glickman et al. (1986) found a single mRNA transcript for apoB regardless of the form of apoB (apoB100 or apoB48) synthesized in the liver or intestine. Hospattankar et al. (1986) presented some immunologic data suggesting that the 2 proteins share a common carboxyl region sequence. Chen et al. (1986) determined the complete cDNA and amino acid sequence of apoB100. Knott et al. (1986) reported the primary structure of apolipoprotein B. The precursor has 4,563 amino acids; the mature apoB100 has 4,536 amino acid residues. This represents a very large mRNA of more than 16 kb. Law et al. (1986) also provided the complete nucleotide and derived amino acid sequence of apoB100 from a study of cDNA. Strong evidence that apoB100 and apoB48 are products of the same gene was provided by Young et al. (1986). Cladaras et al. (1986) concluded from the sequence of apolipoprotein B100 that apoB48 may result from differential splicing of the same primary apoB mRNA transcript. Hardman et al. (1987) found that mature, circulating B48 is homologous over its entire length (estimated to be between 2,130 and 2,144 amino acid residues) with the amino-terminal portion of B100 and contains no sequence from the carboxyl end of B100. From structural studies, Innerarity et al. (1987) concluded that apoB48 represents the amino-terminal 47% of apoB100 and that the carboxyl terminus of apoB48 is in the vicinity of residue 2151 of apoB100. Chen et al. (1987) deduced that human apolipoprotein B48 is the product of an intestinal mRNA with an in-frame UAA stop codon resulting from a C-to-U change in the codon CAA encoding Gln(2153) in apoB100 mRNA. The carboxyl-terminal ile-2152 of apoB48 purified from chylous ascites fluid has apparently been cleaved from the initial translation product, leaving met-2151 as the new carboxyl-terminus. The organ-specific introduction of a stop codon to an mRNA is an unprecedented finding. Only the sequence that codes B100 is present in genomic DNA. The change from CAA to UAA as codon 2153 of the message is a unique RNA editing process. Higuchi et al. (1988) reported similar findings. ApoB48 contains 2,152 residues compared to 4,535 residues in apoB100. Using a cloned rat cDNA as a probe, Lau et al. (1994) cloned cDNA and genomic sequences of the gene for the human APOB mRNA editing protein (BEDP; 600130). Expression of the cDNA in HepG2 cells resulted in editing of the intracellular apoB mRNA. By Northern blot analysis, they showed that the human BEDP mRNA is expressed exclusively in the small intestine.MAPPING
Law et al. (1985) assigned the APOB gene to chromosome 2 by filter hybridization with DNA from human/mouse somatic cell hybrids. By somatic cell hybrid studies and by in situ hybridization, Knott et al. (1985) assigned the APOB gene to the tip of 2p in ... More on the omim web site
Feb. 2, 2018: Protein entry updated
Automatic update: Uniprot description updated
Dec. 19, 2017: Protein entry updated
Automatic update: Uniprot description updated
Nov. 23, 2017: Protein entry updated
Automatic update: Uniprot description updated
March 16, 2016: Protein entry updated
Automatic update: OMIM entry 107730 was added.