Fig. 1. Yeast two-hybrid interaction between IIGP and mHk3. A, The interaction between IIGP, the GTPase negative mutant IIGP_S83N, controls (lamin, Drosophila Bicoid) or the other members of the 47 kDa GTPase protein family and full-length mHk3 were analyzed by growth on selective medium lacking leucine or for lacZ reporter activity. A Leu⁺ß-gal⁺ (Leu⁺lacZ⁺) phenotype is indicated by +, while – indicates no detectable reporter activity. (B) Schematic depiction of the domains in mHk3. The N-terminal region (hatched) harbors a microtubule binding domain. The four putative central coiled-coil regions are indicated (dark gray) and the C terminus (dotted) depicts the region involved in Golgi membrane association (Walenta et al., 2001). Truncated mutants of mHk3 were generated and analyzed for interaction with IIGP. ß-Galactosidase activities, reflecting strength of the interactions, were determined by a liquid culture assay and values are given in Miller Units. (C) Schematic depiction of IIGP with the localization of the guanylate-binding domain (black) indicated. Deletion variants of IIGP were tested for interaction with full-length mHk3 by growth on selective medium lacking leucine or for lacZ reporter activity. All analytical experiments were repeated twice with almost identical results.