Serum albumin

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This article is about the family of mammalian albumin proteins. For the human variant, see human serum albumin. For the cow variant, see bovine serum albumin.
Albumin
ALB structure.png
PDB rendering based on 1e7h.
Available structures
PDB Ortholog search: PDBe, RCSB
Identifiers
Symbols ALB ; PRO0883; PRO0903; PRO1341
External IDs OMIM103600 MGI87991 HomoloGene405 ChEMBL: 3253 GeneCards: ALB Gene
RNA expression pattern
PBB GE ALB 211298 s at tn.png
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 NP_033784
Location (UCSC) Chr 4:
74.26 – 74.29 Mb
Chr 5:
90.46 – 90.48 Mb
PubMed search [1] [2]

Serum albumin, often referred to simply as blood albumin, is a globular protein that in humans is encoded by the ALB gene.[1][2][3]

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.

Function[edit]

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[edit]

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.[3]

Properties[edit]

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[edit]

Main article: Albumin

The general structure of albumin is characterized by several long α helices, this allows it to maintain a relatively static shape, something 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.[4]

Serum albumin family
PDB 1ao6 EBI.jpg
Structure of human serum albumin.[5]
Identifiers
Symbol Serum_albumin
Pfam PF00273
Pfam clan CL0282
InterPro IPR014760
SMART SM00103
PROSITE PS51438
SCOP 1ao6
SUPERFAMILY 1ao6

Types[edit]

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[edit]

References[edit]

  1. ^ 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. 
  2. ^ Harper ME, Dugaiczyk A (July 1983). "Linkage of the evolutionarily-related serum albumin and alpha-fetoprotein genes within q11-22 of human chromosome 4". Am. J. Hum. Genet. 35 (4): 565–72. PMC 1685723. PMID 6192711. 
  3. ^ a b "Entrez Gene: albumin". 
  4. ^ 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 Struct. Biol. 3: 6. doi:10.1186/1472-6807-3-6. PMC 166163. PMID 12846933. 
  5. ^ Sugio S, Kashima A, Mochizuki S, Noda M, Kobayashi K (June 1999). "Crystal structure of human serum albumin at 2.5 A resolution". Protein Eng. 12 (6): 439–46. doi:10.1093/protein/12.6.439. PMID 10388840. 

External links[edit]