Mouse S100G protein exhibits properties characteristic of a calcium sensor.

Bovine S100 G (calbindin D9k, small Ca2+-binding protein of the EF-hand superfamily) is considered as a calcium buffer protein; i.e., the binding of Ca2+ practically does not change its general conformation. A set of experimental approaches has been used to study structural properties of apo- and Ca2+-loaded forms of mouse S100 G (81.4% identity in amino acid sequence with bovine S100 G). This analysis revealed that, in contrast to bovine S100 G, the removal of calcium ions increases α-helices content of mouse S100 G protein and enhances its accessibility to digestion by α-chymotrypsin. Furthermore, mouse apo-S100 G is characterized by a decreased surface hydrophobicity and reduced tendency for oligomerization. Such behavior is typical of calcium sensor proteins. Apo-state of mouse S100 G still has rather compact structure, which can be cooperatively unfolded by temperature and GdnHCl. Computational analysis of amino acid sequences of S100 G proteins shows that these proteins could be in a disordered state upon a removal of the bound calcium ions. The experimental data show that, although mouse apo-S100 G is flexible compared to the Ca2+-loaded state, the apo-form is not completely disordered and preserves some cooperatively meting structure. The origin of the unexpectedly high stability of mouse S100 G can be rationalized by an exceptionally strong association of its N- and C-terminal parts containing the EF-hands I and II, respectively. Copyright © 2020 Elsevier Ltd. All rights reserved.

Citation

Sergei E Permyakov, Elena N Yundina, Alexei S Kazakov, Maria E Permyakova, Vladimir N Uversky, Eugene A Permyakov. Mouse S100G protein exhibits properties characteristic of a calcium sensor. Cell calcium. 2020 May;87:102185

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PMID: 32114281

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