Differential regulation of vertebrate myosins I and II.
Cell motility events require movement of the cytoskeleton. Actin-based movement is catalyzed by the mechanoenzyme myosin, which translocates toward the barbed end of actin filaments in an ATP-dependent fashion. There are two subclasses of myosin with different structures and functions: conventional filamentous myosin (myosin II) and monomeric myosin I. Vertebrate non-muscle myosins I and II function as similar actin motors in vitro, catalyzing virtually identical actin-activated MgATP hydrolysis and motility. The functional diversification of these two enzymes results from their differential regulation. Calcium and tropomyosin, which activate the MgATP hydrolysis and motility of vertebrate non-skeletal muscle myosin II proteins, inhibit vertebrate (brush border) myosin I. The activities and regulation of brush border myosin I provide insight into conserved and unique features of the myosin mechanoenzymes and suggest how the functions of myosins I and II are divided in vertebrate cells. Brush border myosin I as an enzyme also contributes to our understanding of the molecular mechanism of motility.
Collins
K
K
M.I.T. and Whitehead Institute for Biomedical Research, Cambridge, MA 02142.
Matsudaira
P
P
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002465:Cell Movement; D008871:Microvilli / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D014335:Tropomyosin / Q000378:metabolism; D014714:Vertebrates
D014335:Tropomyosin; D009218:Myosins; D002118:Calcium