S100β contains one unusual and one canonical Ca2+-binding motif. In this study, we measured Ca2+-binding and ensuing conformational changes of recombinant S100β (rS100β) and of two mutant forms in which either the canonical loop was inactivated (NoEF) or the unusual one replaced by a canonical one (Caloops). Caloops binds two Ca2+ per monomer with a 3-fold higher affinity than rS100β; the affinity of NoEF was too low for accurate direct determination. All three proteins bind 3-4 Zn2+ per monomer. Tyrosine 17 fluorescence spectra showed a decrease of intensity upon binding of Ca2+ to the three proteins and an increase upon binding of Zn2+ to rS100β and NoEF but not in Caloops. The fluorescence change as a function of the Ca2+ concentration yielded half-maximal changes ([Ca2+]05) at 1.7, 11.3 and 0.55 mM free Ca2+ for rS100β, NoEF and Caloops, respectively. Our data demonstrate that in S100β alterations in one site can affect the Ca2+ binding properties of the other site.
|Number of pages||5|
|Journal||Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology|
|State||Published - Dec 5 1997|
Bibliographical noteFunding Information:
These studies were supported in part by the SNSF grant 3100-037575.93 (to JAC) and NIH grant AG10208 (to LVE).
- Calcium binding
- Conformational change
- EF-hand calcium binding protein
- S100 protein
- Tyrosine fluorescence
- Zinc binding
ASJC Scopus subject areas
- Structural Biology
- Molecular Biology