Journal article
Actin Hydrophobic Loop 262–274 and Filament Nucleation and Elongation
Journal of molecular biology, Vol.375(3), pp.793-801
2008
DOI: 10.1016/j.jmb.2007.10.076
PMID: 18037437
Abstract
The importance of actin hydrophobic loop 262–274 dynamics to actin polymerization and filament stability has been shown recently with the use of the yeast mutant actin L180C/L269C/C374A, in which the hydrophobic loop could be locked in a “parked” conformation by a disulfide bond between C180 and C269. Such a cross-linked globular actin monomer does not form filaments, suggesting nucleation and/or elongation inhibition. To determine the role of loop dynamics in filament nucleation and/or elongation, we studied the polymerization of the cross-linked actin in the presence of cofilin, to assist with actin nucleation, and with phalloidin, to stabilize the elongating filament segments. We demonstrate here that together, but not individually, phalloidin and cofilin co-rescue the polymerization of cross-linked actin. The polymerization was also rescued by filament seeds added together with phalloidin but not with cofilin. Thus, loop immobilization
via cross-linking inhibits both filament nucleation and elongation. Nevertheless, the conformational changes needed to catalyze ATP hydrolysis by actin occur in the cross-linked actin. When actin filaments are fully decorated by cofilin, the helical twist of filamentous actin (F-actin) changes by ∼
5° per subunit. Electron microscopic analysis of filaments rescued by cofilin and phalloidin revealed a dense contact between opposite strands in F-actin and a change of twist by ∼
1° per subunit, indicating either partial or disordered attachment of cofilin to F-actin and/or competition between cofilin and phalloidin to alter F-actin symmetry. Our findings show an importance of the hydrophobic loop conformational dynamics in both actin nucleation and elongation and reveal that the inhibition of these two steps in the cross-linked actin can be relieved by appropriate factors.
Details
- Title: Subtitle
- Actin Hydrophobic Loop 262–274 and Filament Nucleation and Elongation
- Creators
- Alexander Shvetsov - Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USAVitold E Galkin - Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-0733, USAAlbina Orlova - Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-0733, USAMartin Phillips - Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USASarah E Bergeron - Department of Biochemistry, University of Iowa College of Medicine, Iowa City, IA 52242, USAPeter A Rubenstein - Department of Biochemistry, University of Iowa College of Medicine, Iowa City, IA 52242, USAEdward H Egelman - Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA 22908-0733, USAEmil Reisler - Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Resource Type
- Journal article
- Publication Details
- Journal of molecular biology, Vol.375(3), pp.793-801
- DOI
- 10.1016/j.jmb.2007.10.076
- PMID
- 18037437
- NLM abbreviation
- J Mol Biol
- ISSN
- 0022-2836
- eISSN
- 1089-8638
- Publisher
- Elsevier Ltd
- Grant note
- DOI: 10.13039/100007197, name: U.S. Public Health Service, award: GM 077190; DOI: 10.13039/100000001, name: National Science Foundation, award: AR042023, GM33689, MCB 0316269
- Language
- English
- Date published
- 2008
- Academic Unit
- Stead Family Department of Pediatrics; Biochemistry and Molecular Biology; Internal Medicine
- Record Identifier
- 9984025278202771
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