The pH-dependent conformational transition of beta-lactoglobulin modulates the binding of protoporphyrin IX

F Tian, K Johnson, A E Lesar, H Moseley, J Ferguson, I D W Samuel, A Mazzini, L Brancaleon

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

We have investigated the interaction between PPIX and beta-lactoglobulin (beta-lg) as a function of the pH of the solution. beta-Ig is a small globular protein (MW approximate to 18 kDa) with a very well characterized structure that reveals several possible binding sites for ligands. The interaction with beta-lg affects the photophysical properties of PPIX. The shift of PPIX emission maximum, excitation maximum and the increase of the fluorescence intensity is an indicator that binding between the porphyrin and beta-lg occurs. The binding constant appears to be modulated by the pH of the solution. Spectroscopic measurements do not reveal any significant energy transfer between the Trp residues of beta-lg and PPIX, however, fluorescence anisotropy decay measurements confirm the binding and the modulation introduced by the pH of the solution. Since beta-lg has been shown to be stable within the range of pH adopted in our experiments (5.0-9.0), the results suggest that PPIX binds a site affected by the pH of the solution. Because of the crystallographic evidence an obvious site is near the aperture of the interior beta-barrel however an alternative (or concurrent) binding site may still be present. (c) 2005 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)38-46
Number of pages9
JournalBiochimica et Biophysica Acta - General Subjects
Volume1760
DOIs
Publication statusPublished - Jan 2006

Keywords

  • lactoglobulin
  • porphyrin
  • fluorescence spectroscopy
  • binding
  • RESONANCE ENERGY-TRANSFER
  • PHOTODYNAMIC THERAPY
  • FLUORESCENCE
  • BOVINE
  • PROTEIN
  • RETINOL
  • AGGREGATION
  • PORPHYRINS
  • PHOTOPRODUCTS
  • MICROTUBULES

Fingerprint

Dive into the research topics of 'The pH-dependent conformational transition of beta-lactoglobulin modulates the binding of protoporphyrin IX'. Together they form a unique fingerprint.

Cite this