Mutational analyses of Dictyostelium IQGAP-related protein GAPA: Possible interaction with small GTPases in cytokinesis

GAPA is an IQGAP-related protein and is involved in Dictyostelium cytokines is. Since mammalian IQGAPs are effectors for Rae/Cdc42, GAPA is also predic ted to bind to small GTPases, which are to be identified. In this study, mu tant GAPAs were examined for functions in cytokinesis by genetic complement ation of gapA(-) cells. Positively charged side chains of Arg(442) and Lys( 474) of GAPA, predicted to be present on the surface of interaction with sm all GTPases, were found to be essential, suggesting, an interaction between GAPA and putative small GTPase in cytokinesis. Also, results from truncate d GAPAs indicated that almost the entire region of GAPA homologous to IQGAP is required for cytokinesis in Dictyostelium.