In vitro activity differences between proteins of the ADF/cofilin family define two distinct subgroups.
The actin depolymerizing factor (ADF)/cofilins are an essential group of proteins that are important regulators of actin filament turnover in vivo. Although protists and yeasts express only a single member of this family, metazoans express two or more members in many cell types. In cells expressing both ADF and cofilin, differences have been reported in the regulation of their expression, their pH sensitivity, and their intracellular distribution. Each member has qualitatively similar interactions with actin, but quantitative differences have been noted. Here we compared quantitative differences between chick ADF and chick cofilin using several assays that measure G-actin binding, actin filament length distribution, and assembly/disassembly dynamics. Quantitative differences were measured in the critical concentrations of the complexes required for assembly, in the effects of nucleotide and divalent metal on actin monomer binding, in pH-dependent severing, in enhancement of filament minus end off-rates, and in steady-state filament length distributions generated in similar mixtures. Some of these assays were used to compare the activities of several ADF/cofilins from across phylogeny, most of which fall into one of two groups based upon their behavior. The ADF-like group has higher affinities for Mg(2+)-ATP-G-actin than the cofilin-like group and a greater pH-dependent depolymerizing activity.
Chen
Hui
H
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA.
Bernstein
Barbara W
BW
Sneider
Judith M
JM
Boyle
Judith A
JA
Minamide
Laurie S
LS
Bamburg
James R
JR
D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors; D000199:Actins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002645:Chickens; D051345:Destrin; D018260:Gelsolin / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D051339:Actin Depolymerizing Factors; D000199:Actins; C495824:DSTN protein, human; D051345:Destrin; D018260:Gelsolin; D008840:Microfilament Proteins