| The zinc and calcium binding S100B interacts and co localizes with IQGAP 1 during dynamic rearrangement of cell membranes . ^^^ We have identified the IQGAP 1 protein as the major cytoplasmic S100B target protein in different rat and human glial cell lines in the presence of Zn ( 2+ ) and Ca ( 2+ ) . ^^^ Zn ( 2+ ) binding to S100B is sufficient to promote interaction with IQGAP 1 . ^^^ IQ motifs on IQGAP 1 represent the minimal interaction sites for S100B . ^^^ We also provide evidence that , in human astrocytoma cell lines , S100B co localizes with IQGAP 1 at the polarized leading edge and areas of membrane ruffling and that both proteins relocate in a Ca ( 2+ ) dependent manner within newly formed vesicle like structures . ^^^ |