Interactions of all-trans-retinol and long-chain fatty acids with interphotoreceptor retinoid-binding protein

Biochemistry. 1993 Oct 26;32(42):11311-8. doi: 10.1021/bi00093a007.


Interphotoreceptor retinoid-binding protein (IRBP), a predominant protein in the interphotoreceptor matrix of the retina, has been implicated in transfer of retinoids between retinal pigment epithelium and photoreceptor cells. The interactions of IRBP with all-trans-retinol have been studied by three fluorescence-based methods and by measurements of binding of 3[H]-labeled all-trans-retinol to this protein. It was found that IRBP contains two sites with similar but not identical affinities for all-trans-retinol. The dissociation constant of the all-trans-retinol-IRBP complex at the first site was 0.1 microM, which is about 10-fold lower than previously reported values. The second site had about 2.5-fold lower affinity for all-trans-retinol as compared to the first site. Long-chain fatty acids were found in this study to displace all-trans-retinol from the stronger retinol-binding site on IRBP. Displacement of all-trans-retinol was used to study the interactions of fatty acids with this protein. It was found that docosahexaenoic acid (DHA C22:6n-3), an essential fatty acid which plays an important role in vision, had the highest apparent affinity for the site probed on IRBP of all the fatty acids studied.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • Binding, Competitive
  • Cattle
  • Docosahexaenoic Acids / metabolism
  • Docosahexaenoic Acids / pharmacology
  • Fatty Acids, Nonesterified / metabolism*
  • Fatty Acids, Nonesterified / pharmacology
  • Isomerism
  • Kinetics
  • Mathematics
  • Photoreceptor Cells / metabolism*
  • Retina / metabolism
  • Retinol-Binding Proteins / isolation & purification
  • Retinol-Binding Proteins / metabolism*
  • Spectrometry, Fluorescence
  • Tritium
  • Vitamin A / metabolism*


  • Fatty Acids, Nonesterified
  • Retinol-Binding Proteins
  • Tritium
  • Vitamin A
  • Docosahexaenoic Acids