J. Biol. Chem., Vol. 265, Issue 17, 9993-9998, 06, 1990
Regulation of the actin-activated ATPase activity of Acanthamoeba myosin II by copolymerization with phosphorylated and dephosphorylated peptides derived from the carboxyl-terminal end of the heavy chain
C Ganguly, MA Atkinson, AK Attri, V Sathyamoorthy, B Bowers and ED Korn
Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892.
Myosin II from Acanthamoeba castellanii is a conventional myosin composed
of two heavy chains and two pairs of light chains. The amino- terminal
approximately 90 kDa of each heavy chain form a globular head that contains
the ATPase site and an ATP-sensitive actin-binding site. The
carboxyl-terminal approximately 80 kDa of both heavy chains interact to
form a coiled coil, helical rod (through which the molecules self-associate
into bipolar filaments) ending in a short nonhelical tailpiece.
Phosphorylation of 3 serine residues at the tip of the tail (at positions
11, 16, and 21 from the carboxyl terminus) inactivates the actin-activated
Mg2(+)-ATPase activity of myosin II filaments. Previous work had indicated
that the activity of each myosin II molecule in a filament reflects the
global state of phosphorylation of the filament rather than the
phosphorylation state of the molecule itself. We have now purified the
approximately 28-kDa carboxyl-terminal region of the heavy chain lacking
the last two phosphorylation sites, and we have shown that this peptide
copolymerizes with and regulates the actin-activated Mg2(+)-ATPase
activities of native dephosphorylated and phosphorylated myosin II. It can
be concluded from these studies that the biologically relevant enzymatic
activity of myosin II is regulated by a phosphorylation-dependent
conformational change in the myosin filaments.