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Evidence for a conformational change in actin induced by fimbrin (N375) binding.

Hanein D, Matsudaira P, DeRosier DJ - J. Cell Biol. (1997)

Bottom Line: The binding of N375 changes actin, which we interpret as a movement of subdomain 1 away from the bound N375.This change in actin structure may affect its affinity for other actin-binding proteins and may be part of the regulation of the cytoskeleton itself.Difference maps between actin and actin decorated with other proteins provides a way to look for novel structural changes in actin.

View Article: PubMed Central - PubMed

Affiliation: The W.M. Keck Institute for Cellular Visualization and The Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts 02254, USA.

ABSTRACT
Fimbrin belongs to a superfamily of actin cross-linking proteins that share a conserved 27-kD actin-binding domain. This domain contains a tandem duplication of a sequence that is homologous to calponin. Calponin homology (CH) domains not only cross-link actin filaments into bundles and networks, but they also bind intermediate filaments and some signal transduction proteins to the actin cytoskeleton. This fundamental role of CH domains as a widely used actin-binding domain underlines the necessity to understand their structural interaction with actin. Using electron cryomicroscopy, we have determined the three-dimensional structure of F-actin and F-actin decorated with the NH2-terminal CH domains of fimbrin (N375). In a difference map between actin filaments and N375-decorated actin, one end of N375 is bound to a concave surface formed between actin subdomains 1 and 2 on two neighboring actin monomers. In addition, a fit of the atomic model for the actin filament to the maps reveals the actin residues that line, the binding surface. The binding of N375 changes actin, which we interpret as a movement of subdomain 1 away from the bound N375. This change in actin structure may affect its affinity for other actin-binding proteins and may be part of the regulation of the cytoskeleton itself. Difference maps between actin and actin decorated with other proteins provides a way to look for novel structural changes in actin.

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(a) An electron micrograph of an ice-embedded actin filament that was included in the average data set. (b) Computed electron diffraction pattern of the filament shown in a. (c) An electron micrograph of an ice-embedded actin filament decorated with N375  that was included in the average data set. (d) Computed electron diffraction pattern of the filament shown in c. The location of the strong  layer lines are indicated by arrows. Bar, 100 Å.
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Figure 1: (a) An electron micrograph of an ice-embedded actin filament that was included in the average data set. (b) Computed electron diffraction pattern of the filament shown in a. (c) An electron micrograph of an ice-embedded actin filament decorated with N375 that was included in the average data set. (d) Computed electron diffraction pattern of the filament shown in c. The location of the strong layer lines are indicated by arrows. Bar, 100 Å.

Mentions: The Actin-N375 filaments (Fig. 1 c) are wider than the F-actin filaments (Fig. 1 a), which is a visual indication that N375 is present on the decorated filaments. Computed diffraction patterns of individual filaments are shown in Fig. 1, b and d. The four strongest layer lines used for layer line collection are marked with arrows. In general, diffraction patterns of individual decorated filaments showed stronger data on layer lines (2,1), (6,3) and (−5,4), again indicating the presence of N375.


Evidence for a conformational change in actin induced by fimbrin (N375) binding.

Hanein D, Matsudaira P, DeRosier DJ - J. Cell Biol. (1997)

(a) An electron micrograph of an ice-embedded actin filament that was included in the average data set. (b) Computed electron diffraction pattern of the filament shown in a. (c) An electron micrograph of an ice-embedded actin filament decorated with N375  that was included in the average data set. (d) Computed electron diffraction pattern of the filament shown in c. The location of the strong  layer lines are indicated by arrows. Bar, 100 Å.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139807&req=5

Figure 1: (a) An electron micrograph of an ice-embedded actin filament that was included in the average data set. (b) Computed electron diffraction pattern of the filament shown in a. (c) An electron micrograph of an ice-embedded actin filament decorated with N375 that was included in the average data set. (d) Computed electron diffraction pattern of the filament shown in c. The location of the strong layer lines are indicated by arrows. Bar, 100 Å.
Mentions: The Actin-N375 filaments (Fig. 1 c) are wider than the F-actin filaments (Fig. 1 a), which is a visual indication that N375 is present on the decorated filaments. Computed diffraction patterns of individual filaments are shown in Fig. 1, b and d. The four strongest layer lines used for layer line collection are marked with arrows. In general, diffraction patterns of individual decorated filaments showed stronger data on layer lines (2,1), (6,3) and (−5,4), again indicating the presence of N375.

Bottom Line: The binding of N375 changes actin, which we interpret as a movement of subdomain 1 away from the bound N375.This change in actin structure may affect its affinity for other actin-binding proteins and may be part of the regulation of the cytoskeleton itself.Difference maps between actin and actin decorated with other proteins provides a way to look for novel structural changes in actin.

View Article: PubMed Central - PubMed

Affiliation: The W.M. Keck Institute for Cellular Visualization and The Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, Massachusetts 02254, USA.

ABSTRACT
Fimbrin belongs to a superfamily of actin cross-linking proteins that share a conserved 27-kD actin-binding domain. This domain contains a tandem duplication of a sequence that is homologous to calponin. Calponin homology (CH) domains not only cross-link actin filaments into bundles and networks, but they also bind intermediate filaments and some signal transduction proteins to the actin cytoskeleton. This fundamental role of CH domains as a widely used actin-binding domain underlines the necessity to understand their structural interaction with actin. Using electron cryomicroscopy, we have determined the three-dimensional structure of F-actin and F-actin decorated with the NH2-terminal CH domains of fimbrin (N375). In a difference map between actin filaments and N375-decorated actin, one end of N375 is bound to a concave surface formed between actin subdomains 1 and 2 on two neighboring actin monomers. In addition, a fit of the atomic model for the actin filament to the maps reveals the actin residues that line, the binding surface. The binding of N375 changes actin, which we interpret as a movement of subdomain 1 away from the bound N375. This change in actin structure may affect its affinity for other actin-binding proteins and may be part of the regulation of the cytoskeleton itself. Difference maps between actin and actin decorated with other proteins provides a way to look for novel structural changes in actin.

Show MeSH