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Phosphorylation of interphotoreceptor retinoid-binding protein (IRBP)

B Wiggert1, C Lal Kapoor, L Lee

  • 1Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, U.S.A.

Neurochemistry International
|May 27, 2010
PubMed

Insights

Phosphorylation of interphotoreceptor retinoid-binding protein (IRBP) was confirmed in bovine eye matrix. This modification altered IRBP

Area of Science:

  • Biochemistry
  • Ophthalmology
  • Cell Biology

Background:

  • Interphotoreceptor retinoid-binding protein (IRBP) is the main soluble protein in the interphotoreceptor matrix (IPM).
  • IRBP is a potential intercellular vehicle for retinoid transport, crucial for vision.
  • Understanding IRBP's post-translational modifications is key to its function.

Purpose of the Study:

  • To investigate the phosphorylation of IRBP in a crude bovine IPM wash.
  • To characterize the nature and consequences of IRBP phosphorylation.

Main Methods:

  • In vitro phosphorylation using [³²P]ATP.
  • SDS-polyacrylamide gel electrophoresis and autoradiography.
  • Size-exclusion and ion-exchange high-performance liquid chromatography (HPLC).
  • Concanavalin A (Con A)-Sepharose affinity chromatography.

Main Results:

  • IRBP was successfully phosphorylated in the in vitro system.
  • Phosphorylation likely occurred on serine and/or threonine residues.
  • Phosphorylated IRBP exhibited altered binding characteristics to Con A-Sepharose, showing tighter binding.

Conclusions:

  • IRBP undergoes phosphorylation, a modification affecting its properties.
  • The altered Con A binding suggests phosphorylation impacts IRBP's interaction with its environment within the IPM.
  • Further research is needed to elucidate the functional implications of IRBP phosphorylation in retinoid transport and vision.

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