Location of the head-tail junction of myosin.
The tails of double-headed myosin molecules consist of an alpha-helical/coiled-coil structure composed of two identical polypeptides with a heptad repeat of hydrophobic amino acids that starts immediately after a conserved proline near position 847. Both muscle and nonmuscle myosins have this heptad repeat and it has been assumed that proline 847 is physically located at the head-tail junction. We present two lines of evidence that this assumption is incorrect. First, we localized the binding sites of several monoclonal antibodies on Acanthamoeba myosin-II both physically, by electron microscopy, and chemically, with a series of truncated myosin-II peptides produced in bacteria. These data indicate that the head-tail junction is located near residue 900. Second, we compared the lengths of two truncated recombinant myosin-II tails with native myosin-II. The distances from the NH2 termini to the tips of these short tails confirms the rise per residue (0.148 nm/residue) and establishes that the 86-nm tail of myosin-II must start near residue 900. We propose that the first 53 residues of heptad repeat of Acanthamoeba myosin-II and other myosins are located in the heads and the proteolytic separation of S-1 from rod occurs within the heads.
Rimm
D L
DL
Department of Cell Biology and Anatomy, Johns Hopkins School of Medicine, Baltimore, Maryland 21205.
Sinard
J H
JH
Pollard
T D
TD
D000048:Acanthamoeba / Q000235:genetics / Q000378:metabolism; D000818:Animals; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D008854:Microscopy, Electron; D008961:Models, Structural; D009218:Myosins / Q000235:genetics / Q000648:ultrastructure*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000648:ultrastructure; D015183:Restriction Mapping
D011994:Recombinant Proteins; D004247:DNA; D009218:Myosins