Serum albumin

ALB
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 1AO6, 1BJ5, 1BKE, 1BM0, 1E78, 1E7A, 1E7B, 1E7C, 1E7E, 1E7F, 1E7G, 1E7H, 1E7I, 1GNI, 1GNJ, 1H9Z, 1HA2, 1HK1, 1HK2, 1HK3, 1HK4, 1HK5, 1N5U, 1O9X, 1TF0, 1UOR, 1YSX, 2BX8, 2BXA, 2BXB, 2BXC, 2BXD, 2BXF, 2BXG, 2BXH, 2BXI, 2BXK, 2BXL, 2BXM, 2BXN, 2BXO, 2BXP, 2BXQ, 2I2Z, 2I30, 2VDB, 2VUE, 2VUF, 2XSI, 2XVQ, 2XVU, 2XVV, 2XVW, 2XW0, 2XW1, 2YDF, 3A73, 3B9L, 3B9M, 3CX9, 3JQZ, 3JRY, 3LU6, 3LU7, 3LU8, 3SQJ, 3TDL, 3UIV, 4E99, 4EMX, 4G03, 4G04, 4HGK, 4HGM, 4IW1, 4IW2, 4K2C, 4L8U, 4L9K, 4L9Q, 4LA0, 4LB9, 4LB2, 2N0X, 2ESG, 4S1Y, 4N0F, 4Z69, 4N0U, 4K71, 2BXE, 4BKE, 5IJF, 5ID7, 5IFO, 5FUO
Identifiers
Aliases	ALB, blood albumin, ANALBA, FDAH, PRO0883, PRO0903, PRO1341, albumin, Serum albumin
External IDs	OMIM: 103600 MGI: 87991 HomoloGene: 405 GeneCards: ALB
Gene ontology Molecular function • DNA binding • oxygen binding • chaperone binding • zinc ion binding • metal ion binding • fatty acid binding • antioxidant activity • protein binding • drug binding • identical protein binding • enzyme binding • pyridoxal phosphate binding • copper ion binding • lipid binding • toxic substance binding Cellular component • cytoplasm • Golgi apparatus • blood microparticle • myelin sheath • protein complex • extracellular fluid • extracellular region • basement membrane • endoplasmic reticulum • extracellular exosome • platelet alpha granule lumen • nucleus Biological process • lipoprotein metabolic process • sodium-independent organic anion transport • response to platinum ion • hemolysis by symbiont of host erythrocytes • response to nutrient • cellular response to starvation • platelet degranulation • negative regulation of apoptotic process • receptor-mediated endocytosis • response to organic substance • positive regulation of circadian sleep/wake cycle, non-REM sleep • maintenance of mitochondrion location • retina homeostasis • bile acid and bile salt transport • transport • negative regulation of programmed cell death • response to mercury ion • cellular oxidant detoxification Sources:Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	213	11657
Ensembl	ENSG00000163631	ENSMUSG00000029368
UniProt	P02768	P07724
RefSeq (mRNA)	NM_000477	NM_009654
RefSeq (protein)	NP_000468.1	NP_033784.2
Location (UCSC)	Chr 4: 73.4 – 73.42 Mb	Chr 5: 90.46 – 90.48 Mb
PubMed search	[1]	[2]
Wikidata

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Serum albumin, often referred to simply as blood albumin, is an albumin (a type of globular protein) found in vertebrate blood. Human serum albumin is encoded by the ALB gene.^[3][4][5] Other mammalian forms, such as bovine serum albumin, are chemically similar.

Serum albumin is produced by the liver, occurs dissolved in blood plasma and is the most abundant blood protein in mammals. Albumin is essential for maintaining the oncotic pressure needed for proper distribution of body fluids between blood vessels and body tissues; without albumin, the high pressure in the blood vessels would force more fluids out into the tissues. It also acts as a plasma carrier by non-specifically binding several hydrophobic steroid hormones and as a transport protein for hemin and fatty acids. Too much or too little circulating serum albumin may be harmful. Albumin in the urine usually denotes the presence of kidney disease. Occasionally albumin appears in the urine of normal persons following long standing (postural albuminuria).

Function

Albumin functions primarily as a carrier protein for steroids, fatty acids, and thyroid hormones in the blood and plays a major role in stabilizing extracellular fluid volume by contributing to oncotic pressure (known also as colloid osmotic pressure) of plasma.

Because smaller animals (for example rats) function at a lower blood pressure, they need less oncotic pressure to balance this, and thus need less albumin to maintain proper fluid distribution.

Synthesis

Albumin is synthesized in the liver as preproalbumin which has an N-terminal peptide that is removed before the nascent protein is released from the rough endoplasmic reticulum. The product, proalbumin, is in turn cleaved in the Golgi vesicles to produce the secreted albumin.^[5]

Properties

Albumin is a globular, water-soluble, un-glycosylated serum protein of approximate molecular weight of 65,000 Daltons.

Albumin (when ionized in water at pH 7.4, as found in the body) is negatively charged. The glomerular basement membrane is also negatively charged in the body; some studies suggest that this prevents the filtration of albumin in the urine. According to this theory, that charge plays a major role in the selective exclusion of albumin from the glomerular filtrate. A defect in this property results in nephrotic syndrome leading to albumin loss in the urine. Nephrotic syndrome patients are sometimes given albumin to replace the lost albumin.

Structure

The general structure of albumin is characterized by several long α helices allowing it to maintain a relatively static shape, which is essential for regulating blood pressure.

Serum albumin contains eleven distinct binding domains for hydrophobic compounds. One hemin and six long-chain fatty acids can bind to serum albumin at the same time.^[6]

Serum albumin family Structure of human serum albumin.[7] Identifiers Symbol Serum_albumin Pfam PF00273 Pfam clan CL0282 InterPro IPR014760 SMART SM00103 PROSITE PS51438 SCOP 1ao6 SUPERFAMILY 1ao6 Available protein structures: Pfam structures PDB RCSB PDB; PDBe; PDBj PDBsum structure summary

Types

Serum albumin is widely distributed in mammals.

• The human version is human serum albumin.
• Bovine serum albumin, or BSA, is commonly used in immunodiagnostic procedures, clinical chemistry reagents, cell culture media, protein chemistry research (including venom toxicity), and molecular biology laboratories (usually to leverage its non-specific protein binding properties).

See also

• Human serum albumin
• Bovine serum albumin
• Blood plasma fractionation
• Chromatography in blood processing
• Lactalbumin
• Ovalbumin

References

1. "Human PubMed Reference:".
2. "Mouse PubMed Reference:".
3. Hawkins JW, Dugaiczyk A (1982). "The human serum albumin gene: structure of a unique locus". Gene. 19 (1): 55–8. doi:10.1016/0378-1119(82)90188-3. PMID 6292049.
4. Harper ME, Dugaiczyk A (July 1983). "Linkage of the evolutionarily-related serum albumin and alpha-fetoprotein genes within q11-22 of human chromosome 4". American Journal of Human Genetics. 35 (4): 565–72. PMC 1685723. PMID 6192711.
5. "Entrez Gene: albumin".
6. Zunszain PA, Ghuman J, Komatsu T, Tsuchida E, Curry S (July 2003). "Crystal structural analysis of human serum albumin complexed with hemin and fatty acid". BMC Structural Biology. 3: 6. doi:10.1186/1472-6807-3-6. PMC 166163. PMID 12846933.
7. Sugio S, Kashima A, Mochizuki S, Noda M, Kobayashi K (June 1999). "Crystal structure of human serum albumin at 2.5 A resolution". Protein Engineering. 12 (6): 439–46. doi:10.1093/protein/12.6.439. PMID 10388840.

External links

• RCSB Protein Data Bank : Molecule of the Month – Serum Albumin
• Albumin binding prediction