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324  structures 71  species 3  interactions 692  sequences 8  architectures

Family: Serum_albumin (PF00273)

Summary: Serum albumin family

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This is the Wikipedia entry entitled "Albumin". More...

Albumin Edit Wikipedia article

Serum albumin family
PDB 1ao6 EBI.jpg
Structure serum albumin.[1][2]
Identifiers
Symbol Serum_albumin
Pfam PF00273
Pfam clan CL0282
InterPro IPR014760
SMART SM00103
PROSITE PS51438
SCOP 1ao6
SUPERFAMILY 1ao6

The albumins (formed from Latin: albumen[3] "(egg) white; dried egg white") are a family of globular proteins, the most common of which is serum albumin. The albumin family consists of all proteins that are water-soluble, are moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins are commonly found in blood plasma, and are unique from other blood proteins in that they are not glycosylated. Substances containing albumins, such as egg white, are called albuminoids.

A number of blood transport proteins are evolutionarily related, including serum albumin, alpha-fetoprotein, vitamin D-binding protein and afamin.[4][5][6]

Function[edit]

Albumin is the main protein of human blood plasma.[7] It binds water, cations (such as Ca2+, Na+ and K+), fatty acids, hormones, bilirubin, thyroxine (T4) and pharmaceuticals (including barbiturates) - its main function is to regulate the colloidal osmotic pressure of blood. Alpha-fetoprotein (alpha-fetoglobulin) is a fetal plasma protein that binds various cations, fatty acids and bilirubin. Vitamin D-binding protein binds to vitamin D and its metabolites, as well as to fatty acids. The biological role of afamin (alpha-albumin) has not yet been characterised.[citation needed]

Structure[edit]

The 3D structure of human serum albumin has been determined by X-ray crystallography to a resolution of 2.5 Å.[8]

Albumin comprises three homologous domains that assemble to form a heart-shaped molecule.[2] Each domain is a product of two subdomains that possess common structural motifs.[2] The principal regions of ligand binding to human serum albumin are located in hydrophobic cavities in subdomains IIA and IIIA, which exhibit similar chemistry. Structurally, the serum albumins are similar, each domain containing five or six internal disulfide bonds, as shown schematically below:

                    +---+          +----+                        +-----+
                    |   |          |    |                        |     |
 xxCxxxxxxxxxxxxxxxxCCxxCxxxxCxxxxxCCxxxCxxxxxxxxxCxxxxxxxxxxxxxxCCxxxxCxxxx
   |                 |       |      |             |               |
   +-----------------+       +------+             +---------------+
 
C = cysteine, x = any amino acid

Types[edit]

Serum albumin[edit]

Serum albumin is the most abundant blood plasma protein and is produced in the liver and forms a large proportion of all plasma protein. The human version is human serum albumin, and it normally constitutes about 50% of human plasma protein.[7]

Serum albumins are important in regulating blood volume by maintaining the oncotic pressure (also known as colloid osmotic pressure) of the blood compartment.[7] They also serve as carriers for molecules of low water solubility this way isolating their hydrophobic nature, including lipid soluble hormones, bile salts, unconjugated bilirubin, free fatty acids (apoprotein), calcium, ions (transferrin), and some drugs like warfarin, phenobutazone, clofibrate & phenytoin. For this reason, it's sometimes referred as a molecular "taxi". Competition between drugs for albumin binding sites may cause drug interaction by increasing the free fraction of one of the drugs, thereby affecting potency.

Specific types include:

Low albumin (hypoalbuminemia) may be caused by liver disease, nephrotic syndrome, burns, protein-losing enteropathy, malabsorption, malnutrition, late pregnancy, artefact, genetic variations and malignancy.

High albumin (hyperalbuminemia) is almost always caused by dehydration. In some cases of retinol (Vitamin A) deficiency, the albumin level can be elevated to high-normal values (e.g., 4.9 g/dL). This is because retinol causes cells to swell with water (this is also the reason too much Vitamin A is toxic).[9] In lab experiments it has been shown that All-trans retinoic acid down regulates human albumin production[10]

Normal range of human serum albumin in adults (> 3 y.o.) is 3.5 to 5 g/dL. For children less than three years of age, the normal range is broader, 2.9-5.5 g/dL.[11]

Albumin binds to the cell surface receptor Albondin.

Other types[edit]

Other types include the storage protein ovalbumin in egg white, and different storage albumins in the seeds of some plants.

  • Note that the protein 'albumin' is spelled with an "i", while "albumen" with an "e", is the white of an egg, which contains (among other things) several dozen types of albumin (with an 'i'), mostly ovalbumin.

Medical uses[edit]

For patients with low blood volume, there is no evidence that albumin reduces mortality when compared with cheaper alternatives such as normal saline, or that albumin reduces mortality in patients with burns and low albumin levels. Therefore, the Cochrane Collaboration recommends that it not be used, except in clinical trials.[12]

In acoustic droplet vaporization (ADV), albumin is sometimes used as a surfactant. ADV has been proposed as a cancer treatment by means of occlusion therapy.[13]

See also[edit]

References[edit]

  1. ^ 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. 
  2. ^ a b c He XM, Carter DC (1992). "Atomic structure and chemistry of human serum albumin.". Nature 358 (6383): 209–15. doi:10.1038/358209a0. PMID 1630489. 
  3. ^ Historia Naturalis 28, 6, 18. 
  4. ^ Haefliger DN, Moskaitis JE, Schoenberg DR, Wahli W (October 1989). "Amphibian albumins as members of the albumin, alpha-fetoprotein, vitamin D-binding protein multigene family". J. Mol. Evol. 29 (4): 344–54. doi:10.1007/BF02103621. PMID 2481749. 
  5. ^ Schoentgen F, Metz-Boutigue MH, Jollès J, Constans J, Jollès P (June 1986). "Complete amino acid sequence of human vitamin D-binding protein (group-specific component): evidence of a three-fold internal homology as in serum albumin and alpha-fetoprotein". Biochim. Biophys. Acta 871 (2): 189–98. doi:10.1016/0167-4838(86)90173-1. PMID 2423133. 
  6. ^ Lichenstein HS, Lyons DE, Wurfel MM, Johnson DA, McGinley MD, Leidli JC, Trollinger DB, Mayer JP, Wright SD, Zukowski MM (July 1994). "Afamin is a new member of the albumin, alpha-fetoprotein, and vitamin D-binding protein gene family". J. Biol. Chem. 269 (27): 18149–54. PMID 7517938. 
  7. ^ a b c Farrugia A (January 2010). "Albumin usage in clinical medicine: tradition or therapeutic?". Transfus Med Rev 24 (1): 53–63. doi:10.1016/j.tmrv.2009.09.005. PMID 19962575. 
  8. ^ 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): 439–446. doi:10.1093/protein/12.6.439. PMID 10388840. 
  9. ^ Gaull, H; Wright, CE; Gaull, GE (December 1984). "Protective effect of taurine, zinc and tocopherol on retinol-induced damage in human lymphoblastoid cells.". J Nutr. 114 (12): 2256–61. PMID 6502269. 
  10. ^ Suzuki, T; Matsuura, T; Ohkawa, K; Miyamura, T; Okazaki, I; Watanabe, T; Suzuki, T (July 2006). "All-trans retinoic acid down-regulates human albumin gene expression through the induction of C/EBPbeta-LIP". Biochem J. 397 (2): 345–53. doi:10.1042/BJ20051863. PMC 1513275. PMID 16608438. 
  11. ^ "Normal Ranges for Common Laboratory Tests." Rush University
  12. ^ "Human albumin solution for resuscitation and volume expansion in critically ill patients". Cochrane Database Syst Rev (10): CD001208. 2011. doi:10.1002/14651858.CD001208.pub3. PMID 21975732. 
  13. ^ Lo, A. H. (May 2007). "Acoustic droplet vaporization threshold: effects of pulse duration and contrast agent". IEEE Trans Ultrason Ferroelectr Freq Control 54 (5): 933–946. PMID 17523558. 

External links[edit]

This article incorporates text from the public domain Pfam and InterPro IPR014760

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This is the Wikipedia entry entitled "Serum albumin". More...

Serum albumin Edit Wikipedia article

Albumin

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 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 molecular weight 65,000.

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]

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. Examples include:

  • 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]

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

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Literature references

  1. He XM, Carter DC; , Nature 1992;358:209-215.: Atomic structure and chemistry of human serum albumin. PUBMED:1630489 EPMC:1630489


Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR014760

A number of serum transport proteins are known to be evolutionarily related, including albumin, alpha-fetoprotein, vitamin D-binding protein and afamin [PUBMED:2481749, PUBMED:2423133, PUBMED:7517938]. Albumin is the main protein of plasma; it binds water, cations (such as Ca2+, Na+ and K+), fatty acids, hormones, bilirubin and drugs - its main function is to regulate the colloidal osmotic pressure of blood. Alphafeto- protein (alpha-fetoglobulin) is a foetal plasma protein that binds various cations, fatty acids and bilirubin. Vitamin D-binding protein binds to vitamin D and its metabolites, as well as to fatty acids. The biological role of afamin (alpha-albumin) has not yet been characterised. The 3D structure of human serum albumin has been determined by X-ray crystallography to a resolution of 2.8A [PUBMED:1630489]. It comprises three homologous domains that assemble to form a heart-shaped molecule [PUBMED:1630489]. Each domain is a product of two subdomains that possess common structural motifs [PUBMED:1630489]. The principal regions of ligand binding to human serum albumin are located in hydrophobic cavities in subdomains IIA and IIIA, which exhibit similar chemistry. Structurally, the serum albumins are similar, each domain containing five or six internal disulphide bonds, as shown schematically below:
                    +---+          +----+                        +-----+
                    |   |          |    |                        |     |
 xxCxxxxxxxxxxxxxxxxCCxxCxxxxCxxxxxCCxxxCxxxxxxxxxCxxxxxxxxxxxxxxCCxxxxCxxxx
   |                 |       |     |              |               |
   +-----------------+       +-----+              +---------------+

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan Serum_albumin (CL0282), which has the following description:

This superfamily includes serum albumin and related families.

The clan contains the following 2 members:

Serum_albumin VitD-bind_III

Alignments

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(42)
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(11)
RP35
(18)
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  Seed
(42)
Full
(692)
Representative proteomes NCBI
(788)
Meta
(0)
RP15
(11)
RP35
(18)
RP55
(55)
RP75
(248)
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  Seed
(42)
Full
(692)
Representative proteomes NCBI
(788)
Meta
(0)
RP15
(11)
RP35
(18)
RP55
(55)
RP75
(248)
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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

External links

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Pfam alignments:

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Trees

This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

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Curation and family details

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Curation View help on the curation process

Seed source: Prosite
Previous IDs: transport_prot;
Type: Domain
Author: Finn RD
Number in seed: 42
Number in full: 692
Average length of the domain: 168.30 aa
Average identity of full alignment: 26 %
Average coverage of the sequence by the domain: 84.70 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 25.5 25.5
Trusted cut-off 25.8 25.5
Noise cut-off 25.0 25.4
Model length: 178
Family (HMM) version: 15
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Species distribution

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Interactions

There are 3 interactions for this family. More...

Actin Serum_albumin VitD-bind_III

Structures

For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Serum_albumin domain has been found. There are 324 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.

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