Myosin I: a new insight into the mechanism and cellular significance of actin-based motility.
From our work on brush border myosin I structure, activity, regulation, and function, we can begin to understand the significance of the diversification of myosin proteins. While myosin I and II proteins retain conserved elements of structure that may dictate their similar mechanisms of motility and actin-activated MgATPase activity, their unique structures may provide the basis for the distinct localization and regulation of the two myosin types. How does the tropomyosin-inhibited actin-binding site of myosin I differ from that of the tropomyosin-activated myosin II actin-binding site? What elements of the sites of interaction of the 110K-protein and calmodulin contribute to the conserved, light-chain dependent coupling of MgATPase activity to translocation and which confer the novel calcium regulation of dissociation in vitro? It seems that the evolutionary demand for diversification of cellular motility functions has been met, at least in the actin-based system, by the evolution of isoforms tailored in structure, activity, regulation, and localization to serve complementary needs.
Collins
K
K
Whitehead Institute for Biomedical Research, Cambridge, MA.
Sellers
J
J
Matsudaira
P
P
D000199:Actins / Q000502:physiology*; D000818:Animals; D004848:Epithelium / Q000502:physiology; D007422:Intestines / Q000502:physiology; D008871:Microvilli / Q000502:physiology; D009068:Movement; D009218:Myosins / Q000502:physiology*
D000199:Actins; D009218:Myosins