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Structural analysis of the G-box domain of the microcephaly protein CPAP suggests a role in centriole architecture.

Hatzopoulos GN, Erat MC, Cutts E, Rogala KB, Slater LM, Stansfeld PJ, Vakonakis I - Structure (2013)

Bottom Line: Centrioles are evolutionarily conserved eukaryotic organelles composed of a protein scaffold surrounded by sets of microtubules organized with a 9-fold radial symmetry.The G-box comprises a single elongated β sheet capable of forming supramolecular assemblies.Structural and biophysical studies highlight the conserved nature of the CPAP-STIL complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.

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The Role of CPAP/SAS-4 in the Centriole Ultrastructure(A) Schematic top view of the centriolar assembly, showing the SAS-6 cartwheel, pinheads (orange) connecting the cartwheel to microtubule triplets, and our proposed location of CPAP (gray). STIL may act as transporter of SAS-6 and CPAP to the growing centriole.(B) View of an area close to microtubules, boxed in (A). The end of the SAS-6 spoke connects to the pinhead, where Cep135 locates. Cep135 interacts with the CPAP C terminus (green), whereas the CPAP coiled coil projects parallel to the microtubule triplet. The microtubule-interacting epitope of CPAP (A5N) can form connections to the B-tubule and C-tubule.(C) Side view of a centriole section, showing the vertical spacing of SAS-6 spokes as they merge together, the pinhead and A-tubule connection, as well as our proposed fibril of CPAP G-box domains crosslinking cartwheel stacks on the vertical axis.
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fig4: The Role of CPAP/SAS-4 in the Centriole Ultrastructure(A) Schematic top view of the centriolar assembly, showing the SAS-6 cartwheel, pinheads (orange) connecting the cartwheel to microtubule triplets, and our proposed location of CPAP (gray). STIL may act as transporter of SAS-6 and CPAP to the growing centriole.(B) View of an area close to microtubules, boxed in (A). The end of the SAS-6 spoke connects to the pinhead, where Cep135 locates. Cep135 interacts with the CPAP C terminus (green), whereas the CPAP coiled coil projects parallel to the microtubule triplet. The microtubule-interacting epitope of CPAP (A5N) can form connections to the B-tubule and C-tubule.(C) Side view of a centriole section, showing the vertical spacing of SAS-6 spokes as they merge together, the pinhead and A-tubule connection, as well as our proposed fibril of CPAP G-box domains crosslinking cartwheel stacks on the vertical axis.

Mentions: A previous cryo-tomographic study of purified C. reinhardtii basal bodies showed distinct electron densities in the vicinity of the microtubule wall (Li et al., 2012). We propose that CPAP accounts for an elongated density observed there that lies roughly parallel to the microtubule triplet (Figures 4A and 4B). The CPAP C terminus, which interacts with Cep135 (Lin et al., 2013), would be placed close to the A-tubule as part of the overall “pinhead” assembly that connects cartwheels to microtubules, and where Cep135/Bld10p also locates (Hiraki et al., 2007). The 24-nm-long CPAP coiled coil would then stretch approximately to the beginning of the C-tubule, where the CPAP N terminus could form connections through its microtubule associating segments (Hsu et al., 2008). Thus, we propose that CPAP acts as a horizontal “strut,” linking the pinhead with microtubules and reinforcing the overall centriole assembly. It is possible that differences in CPAP length among organisms are related to apparent differences in microtubule tilt with respect to cartwheel spokes; however, further modeling efforts would be required to assess this hypothesis.


Structural analysis of the G-box domain of the microcephaly protein CPAP suggests a role in centriole architecture.

Hatzopoulos GN, Erat MC, Cutts E, Rogala KB, Slater LM, Stansfeld PJ, Vakonakis I - Structure (2013)

The Role of CPAP/SAS-4 in the Centriole Ultrastructure(A) Schematic top view of the centriolar assembly, showing the SAS-6 cartwheel, pinheads (orange) connecting the cartwheel to microtubule triplets, and our proposed location of CPAP (gray). STIL may act as transporter of SAS-6 and CPAP to the growing centriole.(B) View of an area close to microtubules, boxed in (A). The end of the SAS-6 spoke connects to the pinhead, where Cep135 locates. Cep135 interacts with the CPAP C terminus (green), whereas the CPAP coiled coil projects parallel to the microtubule triplet. The microtubule-interacting epitope of CPAP (A5N) can form connections to the B-tubule and C-tubule.(C) Side view of a centriole section, showing the vertical spacing of SAS-6 spokes as they merge together, the pinhead and A-tubule connection, as well as our proposed fibril of CPAP G-box domains crosslinking cartwheel stacks on the vertical axis.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3824074&req=5

fig4: The Role of CPAP/SAS-4 in the Centriole Ultrastructure(A) Schematic top view of the centriolar assembly, showing the SAS-6 cartwheel, pinheads (orange) connecting the cartwheel to microtubule triplets, and our proposed location of CPAP (gray). STIL may act as transporter of SAS-6 and CPAP to the growing centriole.(B) View of an area close to microtubules, boxed in (A). The end of the SAS-6 spoke connects to the pinhead, where Cep135 locates. Cep135 interacts with the CPAP C terminus (green), whereas the CPAP coiled coil projects parallel to the microtubule triplet. The microtubule-interacting epitope of CPAP (A5N) can form connections to the B-tubule and C-tubule.(C) Side view of a centriole section, showing the vertical spacing of SAS-6 spokes as they merge together, the pinhead and A-tubule connection, as well as our proposed fibril of CPAP G-box domains crosslinking cartwheel stacks on the vertical axis.
Mentions: A previous cryo-tomographic study of purified C. reinhardtii basal bodies showed distinct electron densities in the vicinity of the microtubule wall (Li et al., 2012). We propose that CPAP accounts for an elongated density observed there that lies roughly parallel to the microtubule triplet (Figures 4A and 4B). The CPAP C terminus, which interacts with Cep135 (Lin et al., 2013), would be placed close to the A-tubule as part of the overall “pinhead” assembly that connects cartwheels to microtubules, and where Cep135/Bld10p also locates (Hiraki et al., 2007). The 24-nm-long CPAP coiled coil would then stretch approximately to the beginning of the C-tubule, where the CPAP N terminus could form connections through its microtubule associating segments (Hsu et al., 2008). Thus, we propose that CPAP acts as a horizontal “strut,” linking the pinhead with microtubules and reinforcing the overall centriole assembly. It is possible that differences in CPAP length among organisms are related to apparent differences in microtubule tilt with respect to cartwheel spokes; however, further modeling efforts would be required to assess this hypothesis.

Bottom Line: Centrioles are evolutionarily conserved eukaryotic organelles composed of a protein scaffold surrounded by sets of microtubules organized with a 9-fold radial symmetry.The G-box comprises a single elongated β sheet capable of forming supramolecular assemblies.Structural and biophysical studies highlight the conserved nature of the CPAP-STIL complex.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.

Show MeSH
Related in: MedlinePlus