BIBLIOS

Document type
Journal articles

Document subtype
Full paper

Title
Metal ions modulate the folding and stability of the tumor suppressor protein S100A2

Participants in the publication
Hugo M. Botelho (Author)
Michael Koch (Author)
Günter Fritz (Author)
Cláudio M. Gomes (Author)
Dep. Química e Bioquímica
BioISI

Summary
The EF-hand protein S100A2 is a cell cycle regulator involved in tumorigenesis, acting through regulation of the p53 activation state. Metal ion-free S100A2 is homodimeric and contains two Ca(2+)-binding sites and two Zn(2+)-binding sites per subunit, whereby the Zn(2+) ion binding to one of the sites is coordinated by residues from two homodimers. The effect of selective binding of these metal ions was investigated using site-specific mutants which lacked one or both zinc sites. CD analysis of secondary structure changes on metallation showed that Zn(2+) binding was associated with a decrease in the secondary structure content, whereas Ca(2+) had the opposite effect in two of the three S100A2 mutants studied. The energy of unfolding (DeltaG(U)) of the apo wild-type S100A2 was determined to be 89.9 kJ mol(-1), and the apparent midpoint transition temperature (T(m)(app))) was 58.4 degrees C. In addition, a detailed study of the urea and thermal unfolding of the S100A2 mutants in different metallation states (apo, Zn(2+) and Ca(2+)) was performed. Thermal denaturation experiments showed that Zn(2+) acts as a destabilizer and Ca(2+) as a stabilizer of the protein conformation. This suggests a synergistic effect between metal binding, protein stability and S100A2 biological activity, according to which Ca(2+) activates and stabilizes the protein, the opposite being observed on Zn(2+) binding.


Institution
INSTITUTO DE TECNOLOGIA QUÍMICA E BIOLÓGICA

Where published
FEBS Journal

Publication Identifiers
ISSN - 1742-464X

Publisher
Wiley



Document Identifiers
DOI - https://doi.org/10.1111/j.1742-4658.2009.06912.x
URL - http://dx.doi.org/10.1111/j.1742-4658.2009.06912.x