Complete nucleotide sequence and deduced polypeptide sequence of a nonmuscle myosin heavy chain gene from XXXX : evidence of a hinge in the rodlike tail.

@entity2199 @entity535 @entity16762 @entity20383 @entity35 @entity121
We have completely sequenced a gene encoding the heavy chain of myosin II, a nonmuscle myosin from the soil ameba @entity16762 . The gene spans 6 kb, is split by three small introns, and encodes a 1,509-residue heavy chain polypeptide. The positions of the three introns are largely conserved relative to characterized vertebrate and invertebrate muscle myosin genes. The deduced @entity20383 head @entity535 sequence shows a high degree of similarity with the globular head sequences of the @entity35 embryonic skeletal muscle and @entity2199 unc 54 muscle myosins. By contrast, there is no unique way to align the deduced myosin II rod @entity535 sequence with the rod sequence of these muscle myosins. Nevertheless, the periodicities of hydrophobic and charged residues in the myosin II rod sequence, which dictate the coiled-coil structure of the rod and its associations within the myosin filament, are very similar to those of the muscle myosins. We conclude that this ameba nonmuscle myosin shares with the muscle myosins of vertebrates and invertebrates an ancestral heavy chain gene. The low level of direct sequence similarity between the rod sequences of @entity121 probably reflects a general tolerance for residue changes in the rod domain (as long as the periodicities of hydrophobic and charged residues are largely maintained), the relative evolutionary "ages" of these myosins, and specific differences between the filament properties of @entity121 . Finally, sequence analysis and electron microscopy reveal the presence within the myosin II rodlike tail of a well-defined hinge region where sharp bending can occur. We speculate that this hinge may play a key role in mediating the effect of heavy chain phosphorylation on enzymatic activity.
