Ligandin and aminoazo-dye-binding protein A both bind bilirubin at a single site. Quantitative studies of the interactions using difference spectrophotometry show that at pH 7.0, protein A binds the tetrapyrrole with an association constant (K) greater than or equal to 2 × 10(7) litre/mol, whereas binding by ligandin is slightly weaker (K = 7 × 10(6) litre/mol) at this pH. The protein-bilirubin complexes give rise to absorption and fluorescence spectra quite different from those of unbound bilirubin and also to large Cotton effects. It appears that on binding to both proteins, the ligand is forced into a rigid twisted configuration in a hydrophobic environment. Ligandin and protein A resemble serum albumin in their interactions with bilirubin.
Spectroscopic studies of the binding of bilirubin by ligandin and aminoazo-dye-binding protein A
- Views Icon Views
- PDF LinkPDF
- Share Icon Share
- Cite Icon Cite
E Tipping, B Ketterer, L Christodoulides, G Enderby; Spectroscopic studies of the binding of bilirubin by ligandin and aminoazo-dye-binding protein A. Biochem J 1 July 1976; 157 (1): 211–216. doi: https://doi.org/10.1042/bj1570211
Download citation file: