The C-terminal Tail of UNC-60B (Actin Depolymerizing Factor/Cofilin) Is Critical for Maintaining Its Stable Association with F-actin and Is Implicated in the Second Actin-binding Site

Actin depolymerizing factor (ADF)/cofilin changes the twist of actin filaments by binding two longitudinally associated actin subunits. In the absence of an atomic model of the ADF/cofilin-F-actin complex, we have identified residues in ADF/cofilin that are essential for filament binding. Here, we h...

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Veröffentlicht in:The Journal of biological chemistry 2001-02, Vol.276 (8), p.5952-5958
Hauptverfasser: Ono, S, McGough, A, Pope, B J, Tolbert, V T, Bui, A, Pohl, J, Benian, G M, Gernert, K M, Weeds, A G
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Sprache:eng
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Zusammenfassung:Actin depolymerizing factor (ADF)/cofilin changes the twist of actin filaments by binding two longitudinally associated actin subunits. In the absence of an atomic model of the ADF/cofilin-F-actin complex, we have identified residues in ADF/cofilin that are essential for filament binding. Here, we have characterized the C-terminal tail of UNC-60B (a nematode ADF/cofilin isoform) as a novel determinant for its association with F-actin. Removal of the C-terminal isoleucine (Ile 152 ) by carboxypeptidase A or truncation by mutagenesis eliminated F-actin binding activity but strongly enhanced actin depolymerizing activity. Replacement of Ile 152 by Ala had a similar but less marked effect; F-actin binding was weakened and depolymerizing activity slightly enhanced. Truncation of both Arg 151 and Ile 152 or replacement of Arg 151 with Ala also abolished F-actin binding and enhanced depolymerizing activity. Loss of F-actin binding in these mutants was accompanied by loss or greatly decreased severing activity. All of the variants of UNC-60B interacted with G-actin in an indistinguishable manner from wild type. Cryoelectron microscopy showed that UNC-60B changed the twist of F-actin to a similar extent to vertebrate ADF/cofilins. Helical reconstruction and structural modeling of UNC-60B-F-actin complex reveal how the C terminus of UNC-60B might be involved in one of the two actin-binding sites.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M007563200