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EBs recognize a nucleotide-dependent structural cap at growing microtubule ends.

Maurer SP, Fourniol FJ, Bohner G, Moores CA, Surrey T - Cell (2012)

Bottom Line: By binding close to the exchangeable GTP-binding site, the CH domain is ideally positioned to sense the microtubule's nucleotide state.The same microtubule-end region is also a stabilizing structural cap protecting the microtubule from depolymerization.This insight supports a common structural link between two important biological phenomena, microtubule dynamic instability and end tracking.

View Article: PubMed Central - PubMed

Affiliation: Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.

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Related in: MedlinePlus

A Pseudoatomic Model of the EB Microtubule-Binding Site(A) 8.6 Å reconstruction of the Mal3143-microtubule interface docked with atomic structures of tubulin (Fourniol et al., 2010) (cryo-EM map, gray surface; 2XRP.pdb; α in blue, β in cyan ribbons) and with a homology model of the Mal3 CH domain (see Experimental Procedures; Slep and Vale, 2007) (map, green surface; Mal3 CH atomic model, green ribbons).(B) Lumenal surface of the reconstruction shown in (A). Dotted circles highlight a region where tubulin monomers clearly differ in the EM map, delineated by the M loop, H6-H7 loop, and helix H7: the EM maps show an empty taxol-binding pocket in β-tubulin (Nogales et al., 1999), whereas an extra density is seen in α-tubulin, which corresponds to an insertion in loop S8-S9 specific to α-tubulin. This enables unambiguous assignment of the α- and β- tubulin densities. A schematic of this lumenal view shows the localization of Mal3 CH domain at the corner of four tubulin heterodimers.(C) Schematic view of the outer microtubule surface illustrating that the Mal3-binding interface does not exist at the seam (red arrow).(D) Close-up of the interface (map rendered at a higher threshold compared with B, gray surface; Mal3 CH model, rainbow-colored ribbons). The residue number of the boundaries of the Mal3 CH domain and the C termini of α- and β-tubulin are labeled, as are tubulin helices α2-H4, β3-H3, β3-H12, and β4-H11.See also Figure S2 and Movie S1.
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fig2: A Pseudoatomic Model of the EB Microtubule-Binding Site(A) 8.6 Å reconstruction of the Mal3143-microtubule interface docked with atomic structures of tubulin (Fourniol et al., 2010) (cryo-EM map, gray surface; 2XRP.pdb; α in blue, β in cyan ribbons) and with a homology model of the Mal3 CH domain (see Experimental Procedures; Slep and Vale, 2007) (map, green surface; Mal3 CH atomic model, green ribbons).(B) Lumenal surface of the reconstruction shown in (A). Dotted circles highlight a region where tubulin monomers clearly differ in the EM map, delineated by the M loop, H6-H7 loop, and helix H7: the EM maps show an empty taxol-binding pocket in β-tubulin (Nogales et al., 1999), whereas an extra density is seen in α-tubulin, which corresponds to an insertion in loop S8-S9 specific to α-tubulin. This enables unambiguous assignment of the α- and β- tubulin densities. A schematic of this lumenal view shows the localization of Mal3 CH domain at the corner of four tubulin heterodimers.(C) Schematic view of the outer microtubule surface illustrating that the Mal3-binding interface does not exist at the seam (red arrow).(D) Close-up of the interface (map rendered at a higher threshold compared with B, gray surface; Mal3 CH model, rainbow-colored ribbons). The residue number of the boundaries of the Mal3 CH domain and the C termini of α- and β-tubulin are labeled, as are tubulin helices α2-H4, β3-H3, β3-H12, and β4-H11.See also Figure S2 and Movie S1.

Mentions: Averaging B lattice contacts of the Mal3 CH domain on GTPγS microtubules produced an 8.6 Å resolution reconstruction in which the secondary structural elements of tubulin and the CH domain of Mal3 are clearly resolved (Figure 2A, gray and green envelope, respectively; Figure S2; Movie S1). This subnanometer resolution allowed α- and β-tubulins to be distinguished unambiguously (Figure 2B) and a pseudoatomic model of the Mal3-binding site to be generated (Figure 2D). The Mal3 CH domain contacts four different tubulin dimers (Figures 2A and 2C), providing an explanation for how the CH domain distinguishes between B lattice contacts and the microtubule seam: the binding site is formed by two adjacent α-tubulin contacts (toward the microtubule plus end) and two adjacent β-tubulin contacts (toward the minus end). This configuration is not present at the seam where lateral α-β contacts exist (Figure 2C). In binding between protofilaments, the EB footprint is distinct from that of microtubule-based motors kinesin and dynein, which step along the protofilament ridge (Mizuno et al., 2004).


EBs recognize a nucleotide-dependent structural cap at growing microtubule ends.

Maurer SP, Fourniol FJ, Bohner G, Moores CA, Surrey T - Cell (2012)

A Pseudoatomic Model of the EB Microtubule-Binding Site(A) 8.6 Å reconstruction of the Mal3143-microtubule interface docked with atomic structures of tubulin (Fourniol et al., 2010) (cryo-EM map, gray surface; 2XRP.pdb; α in blue, β in cyan ribbons) and with a homology model of the Mal3 CH domain (see Experimental Procedures; Slep and Vale, 2007) (map, green surface; Mal3 CH atomic model, green ribbons).(B) Lumenal surface of the reconstruction shown in (A). Dotted circles highlight a region where tubulin monomers clearly differ in the EM map, delineated by the M loop, H6-H7 loop, and helix H7: the EM maps show an empty taxol-binding pocket in β-tubulin (Nogales et al., 1999), whereas an extra density is seen in α-tubulin, which corresponds to an insertion in loop S8-S9 specific to α-tubulin. This enables unambiguous assignment of the α- and β- tubulin densities. A schematic of this lumenal view shows the localization of Mal3 CH domain at the corner of four tubulin heterodimers.(C) Schematic view of the outer microtubule surface illustrating that the Mal3-binding interface does not exist at the seam (red arrow).(D) Close-up of the interface (map rendered at a higher threshold compared with B, gray surface; Mal3 CH model, rainbow-colored ribbons). The residue number of the boundaries of the Mal3 CH domain and the C termini of α- and β-tubulin are labeled, as are tubulin helices α2-H4, β3-H3, β3-H12, and β4-H11.See also Figure S2 and Movie S1.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3368265&req=5

fig2: A Pseudoatomic Model of the EB Microtubule-Binding Site(A) 8.6 Å reconstruction of the Mal3143-microtubule interface docked with atomic structures of tubulin (Fourniol et al., 2010) (cryo-EM map, gray surface; 2XRP.pdb; α in blue, β in cyan ribbons) and with a homology model of the Mal3 CH domain (see Experimental Procedures; Slep and Vale, 2007) (map, green surface; Mal3 CH atomic model, green ribbons).(B) Lumenal surface of the reconstruction shown in (A). Dotted circles highlight a region where tubulin monomers clearly differ in the EM map, delineated by the M loop, H6-H7 loop, and helix H7: the EM maps show an empty taxol-binding pocket in β-tubulin (Nogales et al., 1999), whereas an extra density is seen in α-tubulin, which corresponds to an insertion in loop S8-S9 specific to α-tubulin. This enables unambiguous assignment of the α- and β- tubulin densities. A schematic of this lumenal view shows the localization of Mal3 CH domain at the corner of four tubulin heterodimers.(C) Schematic view of the outer microtubule surface illustrating that the Mal3-binding interface does not exist at the seam (red arrow).(D) Close-up of the interface (map rendered at a higher threshold compared with B, gray surface; Mal3 CH model, rainbow-colored ribbons). The residue number of the boundaries of the Mal3 CH domain and the C termini of α- and β-tubulin are labeled, as are tubulin helices α2-H4, β3-H3, β3-H12, and β4-H11.See also Figure S2 and Movie S1.
Mentions: Averaging B lattice contacts of the Mal3 CH domain on GTPγS microtubules produced an 8.6 Å resolution reconstruction in which the secondary structural elements of tubulin and the CH domain of Mal3 are clearly resolved (Figure 2A, gray and green envelope, respectively; Figure S2; Movie S1). This subnanometer resolution allowed α- and β-tubulins to be distinguished unambiguously (Figure 2B) and a pseudoatomic model of the Mal3-binding site to be generated (Figure 2D). The Mal3 CH domain contacts four different tubulin dimers (Figures 2A and 2C), providing an explanation for how the CH domain distinguishes between B lattice contacts and the microtubule seam: the binding site is formed by two adjacent α-tubulin contacts (toward the microtubule plus end) and two adjacent β-tubulin contacts (toward the minus end). This configuration is not present at the seam where lateral α-β contacts exist (Figure 2C). In binding between protofilaments, the EB footprint is distinct from that of microtubule-based motors kinesin and dynein, which step along the protofilament ridge (Mizuno et al., 2004).

Bottom Line: By binding close to the exchangeable GTP-binding site, the CH domain is ideally positioned to sense the microtubule's nucleotide state.The same microtubule-end region is also a stabilizing structural cap protecting the microtubule from depolymerization.This insight supports a common structural link between two important biological phenomena, microtubule dynamic instability and end tracking.

View Article: PubMed Central - PubMed

Affiliation: Cancer Research UK London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3LY, UK.

Show MeSH
Related in: MedlinePlus