A group of closely related myosins is characterized by the presence of at least one MyTH/FERM (myosin tail homology; band 4.1, ezrin, radixin, moesin) domain in their C-terminal tails. This domain interacts with a variety of binding partners, and mutations in either the MyTH4 or the FERM domain of myosin VII and myosin XV result in deafness, highlighting the functional importance of each domain. The N-terminal MyTH/FERM region of Dictyostelium myosin VII (M7) has been isolated as a first step toward gaining insight into the function of this domain and its interaction with binding partners. The M7 MyTH4/FERM domain (MF1) binds to both actin and microtubules in vitro, with dissociation constants of 13.7 and 1.7μM, respectively. Gel filtration and UV spectroscopy reveal that MF1 exists as a monomer in solution and forms a well-folded, compact conformation with a high degree of secondary structure. These results indicate that MF1 forms an integrated structural domain that serves to couple actin filaments and microtubules in specific regions of the cytoskeleton.
Bibliographical noteFunding Information:
We thank Dr. Ewa Prochniewicz for expert advice on actin binding measurements, Drs. Holly Goodson (Notre Dame) and Susan Gilbert (RPI) for help with microtubule binding experiments, Dr. Martin Kollmar (Max Planck Institute) for the pDXA-mako 4b expression plasmid, Eunice Song for technical assistance and Drs. Anne Houdusse (Institute Curie) and Gaku Ashiba for many helpful discussions. CD spectroscopy was performed at the Biophysical Spectroscopy Facility, University of Minnesota. We appreciate the excellent assistance with manuscript preparation from Octavian Cornea. This work was supported by National Institutes of Health grants GM046486 (ARRA award) to M.A.T., AR032961 to D.D.T. and F31AG037303 to R.J.M.
- myosin VII