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  Conservation and divergence between cytoplasmic and muscle-specific actin capping proteins: insights from the crystal structure of cytoplasmic Cap32/34 from Dictyostelium discoideum.

Eckert, C., Goretzki, A., Faberova, M., & Kollmar, M. (2012). Conservation and divergence between cytoplasmic and muscle-specific actin capping proteins: insights from the crystal structure of cytoplasmic Cap32/34 from Dictyostelium discoideum. BMC Structural Biology, 12: 12. doi:10.1186/1472-6807-12-12.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-000F-A488-3 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-0027-CAB7-B
Genre: Journal Article

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 Creators:
Eckert, C.1, Author              
Goretzki, A.1, Author              
Faberova, M.1, Author              
Kollmar, M.1, Author              
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1Research Group of Systems Biology of Motor Proteins, MPI for biophysical chemistry, Max Planck Society, ou_578570              

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Free keywords: Capping protein, Actin-binding, Dictyostelium discoideum, Structural flexibility, Cap32/34, CapZ
 Abstract: Background: Capping protein (CP), also known as CapZ in muscle cells and Cap32/34 in Dictyostelium discoideum , plays a major role in regulating actin filament dynamics. CP is a ubiquitously expressed heterodimer comprising an α - and β -subunit. It tightly binds to the fast growing end of actin filaments, thereby functioning as a “ cap ” by blocking the addition and loss of actin subunits. Vertebrates contain two somatic variants of CP, one being primarily found at the cell periphery of non-muscle tissues while the other is mainly localized at the Z-discs of skeletal muscles. Results: To elucidate structural and functional differences between cytoplasmic and sarcomercic CP variants, we have solved the atomic structure of Cap32/34 (32 = β - and 34 = α -subunit) from the cellular slime mold Dictyostelium at 2.2 Å resolution and compared it to that of chicken muscle CapZ. The two homologs display a similar overall arrangement including the attached α -subunit C-terminus ( α -tentacle) and the flexible β -tentacle. Nevertheless, the structures exhibit marked differences suggesting considerable structural flexibility within the α -subunit. In the α -subunit we observed a bending motion of the β -sheet region located opposite to the position of the C-terminal β -tentacle towards the antiparallel helices that interconnect the heterodimer. Recently, a two domain twisting attributed mainly to the β -subunit has been reported. At the hinge of these two domains Cap32/ 34 contains an elongated and highly flexible loop, which has been reported to be important for the interaction of cytoplasmic CP with actin and might contribute to the more dynamic actin-binding of cytoplasmic compared to sarcomeric CP (CapZ). Conclusions: The structure of Cap32/34 from Dictyostelium discoideum allowed a detailed analysis and comparison between the cytoplasmic and sarcomeric variants of CP. Significant structural flexibility could particularly be found within the α -subunit, a loop region in the β -subunit, and the surface of the α -globule where the amino acid differences between the cytoplasmic and sarcomeric mammalian CP are located. Hence, the crystal structure of Cap32/34 raises the possibility of different binding behaviours of the CP variants toward the barbed end of actin filaments, a feature, which might have arisen from adaptation to different environments.

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Language(s): eng - English
 Dates: 2012-06-01
 Publication Status: Published online
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 Rev. Method: Peer
 Identifiers: DOI: 10.1186/1472-6807-12-12
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Title: BMC Structural Biology
Source Genre: Journal
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Pages: - Volume / Issue: 12 Sequence Number: 12 Start / End Page: - Identifier: -