This article is about albumin specific to cows. For the human variant, see
human serum albumin. For the family of mammalian albumins, see
serum albumin.
Bovine serum albumin (BSA or "Fraction V") is a
serum albumin protein derived from cows. It is often used as a protein concentration standard in lab experiments.
The nickname "Fraction V" refers to albumin being the fifth fraction of the original
Edwin Cohn purification methodology that made use of differential solubility characteristics of
plasma proteins. By manipulating solvent concentrations,
pH,
salt levels, and
temperature, Cohn was able to pull out successive "fractions" of
blood plasma. The process was first commercialized with human albumin for medical use and later adopted for production of BSA.
Properties
The full-length BSA precursor polypeptide is 607 amino acids (AAs) in length. An
N-terminal 18-residue
signal peptide is cut off from the precursor protein upon secretion, hence the initial protein product contains 589 amino acid residues. An additional six amino acids are cleaved to yield the mature BSA protein that contains 583 amino acids.[1]
BSA has three homologous but structurally different domains. The domains, named I, II, and III, are broken down into two sub-domains, A and B.[1]
BSA, like other
serum albumins, is critical in providing
oncotic pressure within capillaries, transporting fatty acids,
bilirubin, minerals and hormones, and functioning as both an anticoagulant and an
antioxidant.[9] There are approximately 6 different
long chain fatty acid binding sites on the protein, the three strongest of which are located one per each domain. BSA can also bind other substances such as
salicylate,
sulfonamides,
bilirubin, and other drugs, which bind to “site 1” in subdomain IIA, while
tryptophan,
thyroxine,
octanoate and other drugs that are aromatic in nature bind to “site 2” in subdomain IIIA.[10]
Applications
BSA is often used a model for other serum albumin proteins, especially
human serum albumin, to which it is 76% structurally homologous.[11]
BSA has numerous biochemical applications including
ELISAs (Enzyme-Linked Immunosorbent Assay), immunoblots, and
immunohistochemistry. Because BSA is a small, stable, moderately non-reactive protein, it is often used as a blocker in immunohistochemistry.[12] During immunohistochemistry, which is the process that uses antibodies to identify antigens in cells, tissue sections are often incubated with BSA blockers to bind nonspecific binding sites.[13][14] This binding of BSA to nonspecific binding sites increases the chance that the antibodies will bind only to the antigens of interest.[15] The BSA blocker improves sensitivity by decreasing background noise as the sites are covered with the moderately non-reactive protein.[16][17] During this process, minimization of nonspecific binding of antibodies is essential in order to acquire the highest signal to noise ratio.[16] BSA is also used as a nutrient in cell and microbial culture. In
restriction digests, BSA is used to stabilize some enzymes during the digestion of
DNA and to prevent adhesion of the enzyme to reaction tubes, pipette tips, and other vessels.[18] This
protein does not affect other
enzymes that do not need it for stabilization. BSA is also commonly used to determine the quantity of other proteins, by comparing an unknown quantity of protein to known amounts of BSA (see
Bradford protein assay). BSA is used because of its ability to increase signal in assays, its lack of effect in many biochemical reactions, and its low cost, since large quantities of it can be readily purified from bovine blood, a byproduct of the cattle industry. Another use for BSA is that it can be used to temporarily isolate substances that are blocking the activity of the enzyme that is needed, thus impeding polymerase chain reaction (PCR).[19] BSA has been widely used as a template to synthesize nanostructures [20] and determining the toxic or beneficial effects of metal ions and their complexes.[21]
BSA is also the main constituent of
fetal bovine serum, a common cell culture medium.
^Ge S, Kojio K, Takahara A, Kajiyama T (1998). "Bovine serum albumin adsorption onto immobilized organotrichlorosilane surface: influence of the phase separation on protein adsorption patterns". Journal of Biomaterials Science. Polymer Edition. 9 (2): 131–150.
doi:
10.1163/156856298x00479.
PMID9493841.
^Peters T (1975). Putman FW (ed.). The Plasma Proteins. Academic Press. pp. 133–181.
^
abcdefghijklmPutnam FW (1975). The Plasma Proteins: Structure, Function and Genetic Control. Vol. 1 (2nd ed.). New York: Academic Press. pp. 141, 147.
ASINB007ESU1JQ.
^Axelsson I (May 1978). "Characterization of proteins and other macromolecules by agarose gel chromatography". Journal of Chromatography A. 152 (1): 21–32.
doi:
10.1016/S0021-9673(00)85330-3.
^Chen CB, Hammo B, Barry J, Radhakrishnan K (July 2021). "Overview of Albumin Physiology and its Role in Pediatric Diseases". Current Gastroenterology Reports. 23 (8): 11.
doi:
10.1007/s11894-021-00813-6.
PMID34213692.
^"Serum Albumins and Allergies". Structural Biology Knowledgebase. National Institute of General Medical Sciences of the National Institutes of Health. October 2013. Archived from
the original on 2021-10-23. Retrieved 2017-03-29.
^Rahmani T, Hajian A, Afkhami A, Bagheri H (2018). "A novel and high performance enzyme-less sensing layer for electrochemical detection of methyl parathion based on BSA templated Au–Ag bimetallic nanoclusters". New Journal of Chemistry. 42 (9): 7213–22.
doi:
10.1039/C8NJ00425K.
^Zavalishin MN, Pimenov OA, Belov KV, Khodov IA, Gamov GA (November 2023). "Chemical equilibria in aqueous solutions of H[AuCl4] and bovine or human serum albumin". Journal of Molecular Liquids. 389: 122914.
doi:
10.1016/j.molliq.2023.122914.
Further reading
Hirayama K, Akashi S, Furuya M, Fukuhara K (December 1990). "Rapid confirmation and revision of the primary structure of bovine serum albumin by ESIMS and Frit-FAB LC/MS". Biochemical and Biophysical Research Communications. 173 (2): 639–646.
doi:
10.1016/S0006-291X(05)80083-X.
PMID2260975.
Wise SA, Watters RL (2010-06-30).
"Bovine Serum Albumin (7 % Solution)"(pdf). Certificate of Analysis. United States National Institute of Standards & Technology. Retrieved 2011-12-22.