Cofilin is an essential component of the yeast cortical cytoskeleton.

Abstract

Abstract. We have biochemically identified the Saccharomyces cerevisiae homologue of the mammalian actin binding protein cofilin. Cofilin and related proteins isolated from diverse organisms are low molecular weight proteins (15-20 kD) that possess several activities in vitro. All bind to monomeric actin and sever filaments, and some can stably associate with filaments. In this study, we demonstrate using viscosity, sedimentation, and actin assembly rate assays that yeast cofilin (16 kD) possesses all of these properties. Cloning and sequencing of the S. cerevisiae cofilin gene (COF1) revealed that yeast cofilin is 41% identical in amino acid sequence to mammalian cofilin and, surprisingly, has homology to a protein outside the family of cofilin-like proteins. The NH2-terminal 16 kD of Abplp, a 65-kD yeast protein identified by its ability to bind to actin filaments, is 23 % identical to yeast cofilin. Immunofluorescence experiments showed that, like Abplp, cofilin is associated with the membrane actin cytoskeleton. A complete disruption of the COF1 gene was created in diploid cells. Sporulation and tetrad analysis revealed that yeast cofilin has an essential function in vivo. Although Abplp shares sequence similarity with cofilin and has the same distribution as cofilin in the cell, multiple copies of the ABP1 gene cannot compensate for the loss of cofilin. Thus, cofilin and Abplp are structurally related but functionally distinct components of the yeast membrane cytoskeleton.

Cooperation of two actin‐binding proteins, cofilin and Aip1, in Saccharomyces cerevisiae

“…10A,B). As has been previously reported (Moon et al 1993), cofilin is co-localized in cortical actin patches. Thus, both cofilin and Aip1 are co-localized in cortical actin patches in a wild-type strain.…”

The maize actin‐depolymerizing factor, ZmADF3, redistributes to the growing tip of elongating root hairs and can be induced to translocate into the nucleus with actin

“…It is small enough to pass through the nuclear pore by diffusion but if it is complexed to actin before translocation, as cofilin is believed to be in mammalian cells, then a nuclear localization sequence or an auxiliary protein would be necessary. No nuclear localization of Acanthamoeba actophorin (Quirk etal., 1993) or yeast cofilin, even after heat shock (Moon et aL, 1993) has been identified. Moreover, heat shock and DMSO induction of mammalian cells causes the dephosphorylation of cofilin which is a prerequisite to its nuclear translocation (Ohta et aL, 1989).…”

Ultrastructure of the yeast actin cytoskeleton and its association with the plasma membrane.

“…The actin binding proteins Abplp and cofilin have been shown by indirect immunofluorescence light microscopy to colocalize exclusively with the cortical actin cytoskeleton (Drubin et al, 1988;Moon et al, 1993). To confirm that the dense, cortical actin patches observed in the electron microscope are the same cortical structures observed by immunofluorescence, affinity-purified antibodies to Abplp and cofilin along with antibodies against actin were used in immunoelectron microscopy double-labeling experiments.…”

“…Production, purification, and characterization of afl~uity-purified, polyclonal rabbit antibodies to ~ and Abplp have been described previously (Drubin et al, 1988), as have antibodies to cofifin (Moon et al, 1993).…”

“…Immunofluorescence light microscopy localization of these yeast actin binding proteins showed association with actin in vivo, but often also revealed differential localization to actin cables or cortical patches. For example, the nonessential actin binding protein Abplp, as well as the essential actin filament severing protein cofilin, are localized to cortical actin patches and not to actin cables (Drubin et al, 1988;Moon et al, 1993). Tropomyosin, which binds to filamentous actin in a divalent cation-dependent manner, is localized to cables of actin but not to cortical patches (Liu and Bretscher, 1989).…”