Abstract
S100B, a member of S100 family, contains various biological activities in the human body. There are two EF-hand motifs, which may interact with calcium ions, in the protein. Upon calcium binding, S100B undergoes conformational changes to expose a hydrophobic surface as a binding site for various target proteins. For example, the target proteins such as Siah-1, Skp-1 and Ebi associate with Ca2+-S100B and subsequently adjust the expression level of β-catenin and the transcription activity of Tcf/LEF. Several studies indicate that S100 proteins may interact with the SGS domain of SIP to inhibit β-catenin degradation and enhance the proliferation of certain cancer cells. In this thesis, we determine the solution structure of Ca2+-S100B in complex and study its interaction with SIP using ITC and fluorescence spectroscopy. By using a series of 3D NMR experiments, the backbone and side chain resonaces were alomost completely assigned. HSQC titration experiments indicate the residues on one protein with significant chemical shift perturbation after associating with its binding partner. The chemical shift perturbation data on both S100B and SIP proteins serve as the input constraints for HADDOCK calculation. The atomic coordinates of S100B in complex calculated in the study were docked with the published structure of SIP189-219 bound to S100A6. The result reveals that the complex structure of S100B-SIP189-219 is more expanded then that of S100B-SIP189-219.