Binding of retinoids and beta-carotene to beta-lactoglobulin. Influence of protein modifications

Biochim Biophys Acta. 1991 Sep 20;1079(3):316-20. doi: 10.1016/0167-4838(91)90075-b.


The binding of retinol, retinyl acetate, retinoic acid and beta-carotene to native, esterified and alkylated beta-lactoglobulin was followed by quenching of tryptophan fluorescence. Three studied retinoids bind to native or modified beta-lactoglobulin in 1:1 molar ratios, with apparent dissociation constants in the range of 10(-8) M. The maximum tryptophan fluorescence quenching of unmodified beta-lactoglobulin by beta-carotene is observed at the ligand/protein ratio of 1:2. Esterification and alkylation of beta-lactoglobulin shift the ratio of beta-carotene/protein to 1:1. In all the cases, except for retinoic acid binding to N-ethyllysyl-BLG, the performed chemical modifications of beta-lactoglobulin enhance protein binding affinity. Measured apparent dissociation constants of beta-carotene complexes with native and modified beta-lactoglobulin are an order of magnitude lower from binding constants of other studied retinoids.

MeSH terms

  • Carotenoids / metabolism*
  • Diterpenes
  • Kinetics
  • Lactoglobulins / metabolism*
  • Protein Binding
  • Retinoids / metabolism*
  • Retinyl Esters
  • Spectrometry, Fluorescence
  • Tretinoin / metabolism
  • Vitamin A / analogs & derivatives
  • Vitamin A / metabolism
  • beta Carotene


  • Diterpenes
  • Lactoglobulins
  • Retinoids
  • Retinyl Esters
  • beta Carotene
  • Vitamin A
  • Carotenoids
  • retinol acetate
  • Tretinoin