Fig. 3. Characterization of isolated clones from a yeast two-hybrid screening of a C. elegans cDNA library with unc-45 cDNA. (A) Two of the clones identified from yeast two-hybrid screens. UNC-45 from a full-length cDNA (pDP#WA036) interacts with the products of fragments of two different myosin cDNAs, NMY-2 and HUM-2. The TPR domain alone was tested and showed no interaction with either NMY-2 or HUM-2. (B) Quantitative ß-gal assay for the yeast two-hybrid clones. (C) Diagram of a conventional myosin II molecule, showing the ATP and actin binding sites in the head domain, IQ motif (light chain and calmodulin binding sequence) in the neck domain and the coiled-coil tail domain. Schematic diagram of MHC B and two myosins identified from the yeast two-hybrid screens that interact with UNC-45. HUM-2 is a type V myosin and the identified cDNA fragment encodes a 140 amino acid segment located in the head domain (striped shading). NMY-2 is a non-muscle type II myosin and a region of 530 amino acids (striped shading) located mostly in the head domain interacts with UNC-45. Note that these two identified regions overlap in the highly conserved head domain as indicated. In UNC-54, the portion of the molecule that is sufficient to localize UNC-45 to the body wall muscle thick filaments is indicated by checked shading. Detailed domain analysis of NMY-2 is not available.