Binding of Ca2+ and Zn2+ to Human Nuclear S100A2 and Mutant Proteins

摘要: The Ca2+-binding protein S100A2 is an unusual member of the S100 family, characterized by its nuclear localization and down-regulated expression in tumorigenic cells. In this study, we investigated properties human recombinant (wtS100A2) two mutants which amino-terminal site I (N mutant) addition carboxyl-terminal II (NC were replaced canonical loop (EF-site) α-parvalbumin. Size exclusion chromatography circular dichroism showed that, irrespective state cation binding, wtS100A2 are dimers rich α-helical structure. Flow dialysis revealed that binds four Ca2+ atoms per dimer with pronounced positive cooperativity. Both also bind but a higher affinity than negative binding first ions to N mutant occurred 100-fold 2-fold increase for last ions. A further 2–3-fold was observed respective steps NC mutant. Hummel-Dryer method demonstrated wild type Zn2+ similar affinity. Fluorescence difference spectrophotometry induces considerable conformational changes, mostly attributable changes microenvironment Tyr76 located II. enhancement 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic acid clearly indicated induce hydrophobic patch at surface wtS100A2, which, as calmodulin, may be instrumental regulatory role nucleus.