Document Detail

Role of intermonomer ionic bridges in the stabilization of the actin filament.
MedLine Citation:
PMID:  18945676     Owner:  NLM     Status:  MEDLINE    
Filament formation is required for most of the functions of actin. However, the intermonomer interactions that stabilize F-actin have not been elucidated because of a lack of an F-actin crystal structure. The Holmes muscle actin model suggests that an ionic interaction between Arg-39 of one monomer and Glu-167 of an adjacent monomer in the same strand contributes to this stabilization. Yeast actin has an Ala-167 instead. F-actin molecular dynamics modeling predicts another interaction between Arg-39 of one monomer and Asp-275 of an opposing strand monomer. In Toxoplasma gondii actin, which forms short stubby filaments, the Asp-275 equivalent is replaced by Arg leading to a potential filament-destabilizing charge-charge repulsion. Using yeast actin, we tested the effect of A167E as a potential stabilizer and A167R and D275R as potential filament disruptors. All mutations caused abnormal growth and mitochondrial malfunction. A167E and D275R actins polymerize normally and form relatively normal appearing filaments. A167R nucleates filaments more slowly and forms filament bundles. The R39D/A167R double mutant, which re-establishes an ionic bond in the opposite orientation, reverses this polymerization and bundling defect. Stoichiometric amounts of yeast cofilin have little effect on wild-type and A167E filaments. However, D275R and A167R actin depolymerization is profound with cofilin. Although our results suggest that disruption of an interaction between Arg-39 and Asp-275 is not sufficient to cause fragmentation, it suggests that it changes filament stability thereby disposing it for enhanced cofilin depolymerizing effects. Ala-167 results demonstrate the in vivo and in vitro importance of another potential Arg-39 ionic interaction.
Ema Stokasimov; Melissa McKane; Peter A Rubenstein
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2008-10-21
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  283     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2008 Dec 
Date Detail:
Created Date:  2008-12-08     Completed Date:  2009-02-19     Revised Date:  2010-09-21    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  34844-54     Citation Subset:  IM    
Department of Biochemistry, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
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MeSH Terms
Actin Depolymerizing Factors / chemistry
Actins / chemistry
Alanine / chemistry
Arginine / chemistry
Aspartic Acid / chemistry
DNA Primers / chemistry
Microfilaments / chemistry*
Models, Molecular
Molecular Conformation
Protein Binding
Toxoplasma / metabolism
Grant Support
Reg. No./Substance:
0/Actin Depolymerizing Factors; 0/Actins; 0/DNA Primers; 0/Ions; 56-41-7/Alanine; 56-84-8/Aspartic Acid; 74-79-3/Arginine

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