Actin depolymerizing factor stabilizes an existing state of F-actin and can change the tilt of F-actin subunits.
Proteins in the actin depolymerizing factor (ADF)/cofilin family are essential for rapid F-actin turnover, and most depolymerize actin in a pH-dependent manner. Complexes of human and plant ADF with F-actin at different pH were examined using electron microscopy and a novel method of image analysis for helical filaments. Although ADF changes the mean twist of actin, we show that it does this by stabilizing a preexisting F-actin angular conformation. In addition, ADF induces a large ( approximately 12 degrees ) tilt of actin subunits at high pH where filaments are readily disrupted. A second ADF molecule binds to a site on the opposite side of F-actin from that of the previously described ADF binding site, and this second site is only largely occupied at high pH. All of these states display a high degree of cooperativity that appears to be an integral part of F-actin.
Galkin
V E
VE
Department of Biochemistry and Molecular Genetics, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
Orlova
A
A
Lukoyanova
N
N
Wriggers
W
W
Egelman
E H
EH
D051339:Actin Depolymerizing Factors; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D051345:Destrin; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D011817:Rabbits
D051339:Actin Depolymerizing Factors; D000199:Actins; C495824:DSTN protein, human; D051345:Destrin; D008840:Microfilament Proteins