A logical sequence search for S100B target proteins

The EF-hand calcium-binding protein S100B has been shown to interact in vitro in a calcium-sensitive manner with many substrates. These potential S100B target proteins have been screened for the preservation of a previously identified consensus sequence across species. The results were compared to known structural and in vitro properties of the proteins to rationalize choices for potential binding partners. Our approach uncovered four oligomeric proteins tubulin (alpha and beta), glial fibrillary acidic protein (GFAP), desmin, and vimentin that have conserved regions matching the consensus sequence. In the type III intermediate filament proteins (GFAP, vimentin, and desmin), this region corresponds to a portion of a coiled-coil (helix 2A), the structural element responsible for their assembly. In tubulin, the sequence matches correspond to regions of alpha and beta tubulin found at the alpha beta tubulin interface. In both cases, these consensus sequence matches provide a logical explanation for in vitro observations that S100B is able to inhibit oligomerization of these proteins.