Association of hemin with protein 4.1 as compared to spectrin and actin

Irit Solar, Nurith Shaklai*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The interaction of hemin with protein 4.1 isolated from red cell membrane cytoskeleton has been studied. Spectrophotometric titration has shown one strong binding site and additional lower affinity sites for hemin. From fluorescence quenching data an association binding constant of 1.3 · 107 M-1 has been calculated for the primary site. The conformation of cytoskeletal proteins after hemin binding was followed by the use of far UV circular dichroism and compared to that of the serum hemin trap, albumin. The secondary structure of albumin was unchanged in the presence of high hemin concentrations. Both spectrin and actin lost their conformation upon hemin binding in a ligand-concentration and time-dependent manner. Unlike spectrin and actin, the secondary structure of protein 4.1 was unaffected by hemin binding to the primary site, but, at higher hemin concentrations, some reduction in the ellipticity of protein 4.1 appeared. The findings of this study suggest that protein 4.1 may serve as the cytoskeletal temporary sink for small amounts of membrane-intercalated hemin similarly to the function of albumin in the serum. However, an increased release of hemin under pathological conditions may cause hemin association with the cytoskeletal proteins and as a result the cell membrane is expected to be distorted.

Original languageEnglish
Pages (from-to)199-204
Number of pages6
JournalBBA - Biomembranes
Issue number2
StatePublished - 7 Aug 1989


  • Actin
  • Circular dichroism
  • Fluorescence
  • Hemin
  • Protein 4.1
  • Spectrin


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