β-Galactoside-binding activity of human galectin-1 at basic pH

Hirotsugu Hiramatsu*, Katsuyuki Takeuchi, Koki Fukuda, Tomohide Nishino

*Corresponding author for this work

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

β-Galactoside-binding activity of human galectin-1 (hGal-1) was evaluated at pH 7-9.5 by fluorescence spectroscopy from the fraction bound to lactose gel (Y) and the lactose binding constant (Kb). Y decreases at pH > 8.2 ± 0.1 in the absence of NaCl, while it is constant in the presence of 150 mM NaCl. On the other hand, Kb is independent of pH and the NaCl concentration at basic pH. Analysis of Raman spectrum has shown that the pKa of Cys residues of hGal-1 is 8.5 ± 0.1 on average, indicating that about 40% of the six Cys residues of hGal-1 would be deprotonated at pH 8.2. The pH dependence of Y is explained by an increase of Coulombic repulsion among negatively charged hGal-1 on the lactose gel surface. This result suggests that Y is not always a good indicator of the β-galactoside-binding activity of galectins, which contain many Cys residues.

Original languageEnglish
Pages (from-to)113-117
Number of pages5
JournalChemical Physics
Volume419
DOIs
StatePublished - 1 Jan 2013

Keywords

  • Fluorescence spectroscopy
  • Galactoside-binding activity
  • Human galectin-1
  • Raman spectroscopy
  • pH dependence

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