The predicted coiled-coil domain of myosin 10 forms a novel elongated domain that lengthens the head.
Myosin 10 contains a region of predicted coiled coil 120 residues long. However, the highly charged nature and pattern of charges in the proximal 36 residues appear incompatible with coiled-coil formation. Circular dichroism, NMR, and analytical ultracentrifugation show that a synthesized peptide containing this region forms a stable single alpha-helix (SAH) domain in solution and does not dimerize to form a coiled coil even at millimolar concentrations. Additionally, electron microscopy of a recombinant myosin 10 containing the motor, the three calmodulin binding domains, and the full-length predicted coiled coil showed that it was mostly monomeric at physiological protein concentration. In dimers the molecules were joined only at their extreme distal ends, and no coiled-coil tail was visible. Furthermore, the neck lengths of both monomers and dimers were much longer than expected from the number of calmodulin binding domains. In contrast, micrographs of myosin 5 heavy meromyosin obtained under the same conditions clearly showed a coiled-coil tail, and the necks were the predicted length. Thus the predicted coiled coil of myosin 10 forms a novel elongated structure in which the proximal region is a SAH domain and the distal region is a SAH domain (or has an unknown extended structure) that dimerizes only at its end. Sequence comparisons show that similar structures may exist in the predicted coiled-coil domains of myosins 6 and 7a and MyoM and could function to increase the size of the working stroke.
Knight
Peter J
PJ
School of Biomedical Sciences, Astbury Centre for Structural Molecular Biology, and School of Biochemistry and Microbiology, University of Leeds, Leeds, LS2 9JT, United Kingdom.
Thirumurugan
Kavitha
K
Xu
Yuhui
Y
Wang
Fei
F
Kalverda
Arnout P
AP
Stafford
Walter F
WF
Sellers
James R
JR
Peckham
Michelle
M
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002147:Calmodulin / Q000737:chemistry; D002417:Cattle; D002942:Circular Dichroism; D019281:Dimerization; D009682:Magnetic Resonance Spectroscopy; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009218:Myosins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D013696:Temperature; D014461:Ultracentrifugation; D014466:Ultraviolet Rays
D002147:Calmodulin; C409064:Myo10 protein, mouse; D010455:Peptides; D011994:Recombinant Proteins; D012965:Sodium Chloride; D009218:Myosins