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© The Rockefeller University Press,
0021-9525/1999//1385 $5.00
The Journal of Cell Biology, Volume 147, Number 7,
, 1999 1385-1390
Brief Report |
Visualization of Head–Head Interactions in the Inhibited State of Smooth Muscle Myosin
taylor{at}bio.fsu.edu
The structural basis for the phosphoryla- tion-dependent regulation of smooth muscle myosin ATPase activity was investigated by forming two- dimensional (2-D) crystalline arrays of expressed unphosphorylated and thiophosphorylated smooth muscle heavy meromyosin (HMM) on positively charged lipid monolayers. A comparison of averaged 2-D projections of both forms at 2.3-nm resolution reveals distinct structural differences. In the active, thiophosphorylated form, the two heads of HMM interact intermolecularly with adjacent molecules. In the unphosphorylated or inhibited state, intramolecular interactions position the actin-binding interface of one head onto the converter domain of the second head, thus providing a mechanism whereby the activity of both heads could be inhibited.
Key Words: myosin light chains phosphorylation two-dimensional crystalline arrays myosin regulation myosin head interactions
© 1999 The Rockefeller University Press
Abbreviations used in this paper: 2-D, two-dimensional; ELC, essential light chain; HMM, heavy meromyosin; MDE, motor domain-essential light chain complex; RLC, regulatory light chain; S1, myosin subfragment 1; S2, subfragment 2 region of the rod.
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