1. Mechanism of Zn 2+ and Ca 2+ Binding to Human S100A1.
- Author
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Baksheeva VE, Roman AY, Villard C, Devred F, Byrne D, Yatoui D, Zalevsky AO, Vologzhannikova AA, Sokolov AS, Permyakov SE, Golovin AV, Shaw GS, Tsvetkov PO, and Zernii EY
- Subjects
- Binding Sites, Humans, Models, Molecular, Protein Binding, Protein Conformation, Signal Transduction, Calcium metabolism, S100 Proteins chemistry, S100 Proteins metabolism, Zinc metabolism
- Abstract
S100A1 is a member of the S100 family of small ubiquitous Ca
2+ -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.- Published
- 2021
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