A mechanism for actin filament severing by malaria parasite actin depolymerizing factor 1 via a low affinity binding interface
Publication Year 2014-02, Volume 289, Issue #7, Page 4043-4054
Journal Title
Journal of Biological Chemistry
Publication Type
Journal Article
Actin depolymerizing factor (ADF)/cofilins are essential regulators of actin turnover in eukaryotic cells. These multifunctional proteins facilitate both stabilization and severing of filamentous (F)-actin in a concentration-dependent manner. At high concentrations ADF/cofilins bind stably to F-actin longitudinally between two adjacent actin protomers forming what is called a decorative interaction. Low densities of ADF/cofilins, in contrast, result in the optimal severing of the filament. To date, how these two contrasting modalities are achieved by the same protein remains uncertain. Here, we define the proximate amino acids between the actin filament and the malaria parasite ADF/cofilin, PfADF1 from Plasmodium falciparum. PfADF1 is unique among ADF/cofilins in being able to sever F-actin but do so without stable filament binding. Using chemical cross-linking and mass spectrometry (XL-MS) combined with structure reconstruction we describe a previously overlooked binding interface on the actin filament targeted by PfADF1. This site is distinct from the known binding site that defines decoration. Furthermore, total internal reflection fluorescence (TIRF) microscopy imaging of single actin filaments confirms that this novel low affinity site is required for F-actin severing. Exploring beyond malaria parasites, selective blocking of the decoration site with human cofilin (HsCOF1) using cytochalasin D increases its severing rate. HsCOF1 may therefore also use a decoration-independent site for filament severing. Thus our data suggest that a second, low affinity actin-binding site may be universally used by ADF/cofilins for actin filament severing.
WEHI Research Division(s)
Infection And Immunity; Systems Biology And Personalised Medicine
Open Access at Publisher's Site
NHMRC Grants
NHMRC/1053801 NHMRC/1018002 NHMRC/1024678
Rights Notice
Refer to copyright notice on published article.

Creation Date: 2014-07-29 03:01:16
Last Modified: 0001-01-01 12:00:00
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