The promiscuous protein binding ability of erythrosine B studied by metachromasy (metachromasia)

Lakshmi Ganesan, Peter Buchwald

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


The present study aims to elucidate aspects of the protein binding ability of erythrosine B (ErB), a poly-iodinated xanthene dye and an FDA-approved food colorant (FD&C Red No. 3), which we have identified recently as a promiscuous inhibitor of protein-protein interactions (PPIs) with a remarkably consistent median inhibitory concentration (IC50) in the 5- to 30-μM range. Because ErB exhibits metachromasy, that is, color change upon binding to several proteins, we exploited this property to quantify its binding to proteins such as bovine serum albumin (BSA) and CD40L (CD154) and to determine the corresponding binding constants (Kd) and stoichiometry (nb) using spectrophotometric methods. Binding was reversible, and the estimated affinities for both protein targets obtained here (Kd values of 14 and 20 μM for BSA and CD40L, respectively) were in good agreement with that expected from the PPI inhibitory activity of ErB. A stoichiometry greater than one was observed both for CD40L and BSA binding (nb of 5-6 and 8-9 for BSA and CD40L, respectively), indicating the possibility of nonspecific binding of the flat and rigid ErB molecule at multiple sites, which could explain the promiscuous PPI inhibitory activity if some of these overlap with the binding site of the protein partner and interfere with the binding.

Original languageEnglish (US)
Pages (from-to)181-189
Number of pages9
JournalJournal of Molecular Recognition
Issue number4
StatePublished - Apr 2013


  • bathochromic shift
  • erythrosine B
  • food colorants
  • Job plot
  • metachromasia
  • promiscuous inhibitors
  • protein binding
  • protein-protein interactions

ASJC Scopus subject areas

  • Molecular Biology
  • Structural Biology


Dive into the research topics of 'The promiscuous protein binding ability of erythrosine B studied by metachromasy (metachromasia)'. Together they form a unique fingerprint.

Cite this