Mechanism of Zn 2+ and Ca 2+ Binding to Human S100A1

authors

  • Baksheeva Viktoriia
  • Roman Andrei
  • Villard Claude
  • Devred François
  • Byrne Deborah
  • Yatoui Dahbia
  • Zalevsky Arth
  • Vologzhanniko Alisa
  • Sokolov Andrey
  • Permyakov Sergei
  • Golovin Andrey
  • Shaw Gary
  • Tsvetkov Philipp
  • Zernii Yu

keywords

  • S100A1
  • Zinc
  • Calcium
  • ESI-MS
  • ITC
  • NanoDSF

abstract

S100A1 is a member of the S100 family of small ubiquitous Ca2+-binding proteins, which participates in the regulation of cell differentiation, motility, and survival. It exists as homo- or heterodimers. S100A1 has also been shown to bind Zn2+, but the molecular mechanisms of this binding are not yet known. In this work, using ESI-MS and ITC, we demonstrate that S100A1 can coordinate 4 zinc ions per monomer, with two high affinity (KD~4 and 770 nm) and two low affinity sites. Using competitive binding experiments between Ca2+ and Zn2+ and QM/MM molecular modeling we conclude that Zn2+ high affinity sites are located in the EF-hand motifs of S100A1. In addition, two lower affinity sites can bind Zn2+ even when the EF-hands are saturated by Ca2+, resulting in a 2Ca2+:S100A1:2Zn2+ conformer. Finally, we show that, in contrast to calcium, an excess of Zn2+ produces a destabilizing effect on S100A1 structure and leads to its aggregation. We also determined a higher affinity to Ca2+ (KD~0.16 and 24 μm) than was previously reported for S100A1, which would allow this protein to function as a Ca2+/Zn2+-sensor both inside and outside cells, participating in diverse signaling pathways under normal and pathological conditions.

more information