Determining the Function of the RGCt Domain of IQG1 in Budding Yeast

Cytokinesis is the final step in cell division, when the mother cell divides into two daughter cells. In budding yeast, IQG1 is an extracellular scaffolding protein that is required for formation and contraction of the actin ring during cytokinesis. The Ras GAP C-terminus domain (RGCt) is one of the four domains found in IQG1. This domain is highly conserved in IQGAP family members, but the function of this domain in budding yeast is currently unknown. Based on data from the human homolog, we suspected that this domain would be required for binding to actin-nucleating proteins called formins; however, our preliminary data shows that this is not the case. Deletion of the RGCt domain is lethal to yeast cells, so its function is essential. To determine binding partners for this domain, we will purify a His-tagged RGCt protein from bacteria, incubate with yeast extracts, and identify candidate interacting proteins by western blotting and novel interactions using mass spectrometry