The location of the high- and low-affinity bilirubin-binding sites on serum albumin: ligand-competition analysis investigated by circular dichroism
Language English Country Netherlands Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
PubMed
23838624
DOI
10.1016/j.bpc.2013.06.004
PII: S0301-4622(13)00093-8
Knihovny.cz E-resources
- Keywords
- BR, BSA, Bilirubin, Binding site, CD, GS, HSA, High affinity, Ibf, Ligand-completion, Low affinity, PSB, RSA, RbSA, SA, SSA, Stereoselectivity, bilirubin, bovine serum albumin, circular dichroism, dCD, difference circular dichroism, gossypol, human serum albumin, ibuprofen, phosphate saline buffer, rabbit serum albumin, rat serum albumin, serum albumin, sheep serum albumin,
- MeSH
- Amino Acid Motifs MeSH
- Bilirubin chemistry metabolism MeSH
- Circular Dichroism MeSH
- Hemin chemistry metabolism MeSH
- Ibuprofen chemistry metabolism MeSH
- Rabbits MeSH
- Rats MeSH
- Humans MeSH
- Ligands * MeSH
- Molecular Conformation MeSH
- Sheep MeSH
- Serum Albumin chemistry metabolism MeSH
- Molecular Docking Simulation MeSH
- Cattle MeSH
- Protein Structure, Tertiary MeSH
- Protein Binding MeSH
- Binding Sites MeSH
- Animals MeSH
- Check Tag
- Rabbits MeSH
- Rats MeSH
- Humans MeSH
- Cattle MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Bilirubin MeSH
- Hemin MeSH
- Ibuprofen MeSH
- Ligands * MeSH
- Serum Albumin MeSH
The locations of three bilirubin (BR)-binding sites with different affinities were identified as subdomains IB, IIA and IIIA for five mammalian serum albumins (SAs): human (HSA), bovine (BSA), rat, (RSA), rabbit (RbSA) and sheep (SSA). The stereoselectivity of a high-affinity BR-binding site was identified in the BR/SA=1/1 system by circular dichroism (CD) spectroscopy, the sites with low affinity to BR were analyzed using difference CD. Site-specific ligand-competition experiments with ibuprofen (marker for subdomain IIIA) and hemin (marker for subdomain IB) did not reveal any changes for the BR/SA=1/1 system and showed a decrease of the bound BR at BR/SA=3/1. Both sites were identified as sites with low affinity to BR. The correlation between stereoselectivity and the arrangement of Arg-Lys residues indicated similarity between the BR-binding sites in subdomain IIIA for all of the SAs studied. Subdomain IB in HSA, BSA, SSA and RbSA has P-stereoselectivity while in RSA it has M-selectivity toward BR. A ligand-competition experiment with gossypol shows a decrease of the CD signal of bound BR for the BR/SA=1/1 system as well as for BR/SA=3/1. Subdomain IIA was assigned as a high-affinity BR-binding site. The P-stereoselectivity of this site in HSA (and RSA, RbSA) was caused by the right-hand localization of charged residues R257/R218-R222, whereas the left-hand orientation of R257/R218-R199 led to the M-stereoselectivity of the primary binding site in BSA (and SSA).
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