The nature of the globular- to fibrous-actin transition.
Actin plays crucial parts in cell motility through a dynamic process driven by polymerization and depolymerization, that is, the globular (G) to fibrous (F) actin transition. Although our knowledge about the actin-based cellular functions and the molecules that regulate the G- to F-actin transition is growing, the structural aspects of the transition remain enigmatic. We created a model of F-actin using X-ray fibre diffraction intensities obtained from well oriented sols of rabbit skeletal muscle F-actin to 3.3 A in the radial direction and 5.6 A along the equator. Here we show that the G- to F-actin conformational transition is a simple relative rotation of the two major domains by about 20 degrees. As a result of the domain rotation, the actin molecule in the filament is flat. The flat form is essential for the formation of stable, helical F-actin. Our F-actin structure model provides the basis for understanding actin polymerization as well as its molecular interactions with actin-binding proteins.
Oda
Toshiro
T
X-ray Structural Analysis Research Team, RIKEN SPring-8 Center, RIKEN Harima Institute, 1-1-1, Kouto, Sayo, Hyogo 679-5148, Japan. toda@spring8.or.jp
Iwasa
Mitsusada
M
Aihara
Tomoki
T
Maéda
Yuichiro
Y
Narita
Akihiro
A
D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism; D002465:Cell Movement; D005973:Glutamine / Q000378:metabolism; D006868:Hydrolysis; D008280:Magnetics; D008958:Models, Molecular; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000737:chemistry; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011817:Rabbits; D014961:X-Ray Diffraction
D000199:Actins; D001704:Biopolymers; D021122:Protein Subunits; D005973:Glutamine