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Structural analysis of the interactions between paxillin LD motifs and alpha-parvin.

Lorenz S, Vakonakis I, Lowe ED, Campbell ID, Noble ME, Hoellerer MK - Structure (2008)

Bottom Line: Cocrystal structures with these LD motifs reveal the molecular details of their interactions with a common binding site on alpha-parvin-CH(C), which is located at the rim of the canonical fold and includes part of the inter-CH domain linker.Surprisingly, this binding site can accommodate LD motifs in two antiparallel orientations.Taken together, these results reveal an unusual degree of binding degeneracy in the paxillin/alpha-parvin system that may facilitate the assembly of dynamic signaling complexes in the cell.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biophysics, University of Oxford, Oxford OX1 3QU, United Kingdom.

ABSTRACT
The adaptor protein paxillin contains five conserved leucine-rich (LD) motifs that interact with a variety of focal adhesion proteins, such as alpha-parvin. Here, we report the first crystal structure of the C-terminal calponin homology domain (CH(C)) of alpha-parvin at 1.05 A resolution and show that it is able to bind all the LD motifs, with some selectivity for LD1, LD2, and LD4. Cocrystal structures with these LD motifs reveal the molecular details of their interactions with a common binding site on alpha-parvin-CH(C), which is located at the rim of the canonical fold and includes part of the inter-CH domain linker. Surprisingly, this binding site can accommodate LD motifs in two antiparallel orientations. Taken together, these results reveal an unusual degree of binding degeneracy in the paxillin/alpha-parvin system that may facilitate the assembly of dynamic signaling complexes in the cell.

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Conservation of α-Parvin Contacting Residues in LD Motifs of Paxillin ParalogsSequence alignment of LD motifs in human paxillin (PAXN), hic-5 (HIC5), and leupaxin (LPXN). Paxillin residues ordered in the crystal structures of the α-parvin-CHC/LD complexes are underlined and those forming contacts with α-parvin-CHC within a radius of 4 Å are boxed.
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fig6: Conservation of α-Parvin Contacting Residues in LD Motifs of Paxillin ParalogsSequence alignment of LD motifs in human paxillin (PAXN), hic-5 (HIC5), and leupaxin (LPXN). Paxillin residues ordered in the crystal structures of the α-parvin-CHC/LD complexes are underlined and those forming contacts with α-parvin-CHC within a radius of 4 Å are boxed.

Mentions: On the basis of our results for α-parvin, we can make two general predictions with respect to LD recognition by CH domains: First, as noted previously (Wang et al., 2008), we propose that the presence of an N-linker helix is a prerequisite for the interaction with LD motifs. In agreement with this hypothesis, it has been reported that α-actinin, whose canonical CH domains lack this structural element, does not interact with paxillin (Nikolopoulos and Turner, 2000). Since the C-terminal region, including the N-linker helix, is highly conserved throughout the parvin family, we speculate that all parvin paralogs may be able to bind LD motifs. Interestingly, γ-parvin was shown to associate with paxillin in vivo (Yoshimi et al., 2006). Available experiments with β-parvin, however, have proved negative to date (Yamaji et al., 2004), although this protein is more similar in sequence to α-parvin than is γ-parvin (Figure 1C). Second, on the basis of the analysis of differential binding of α-parvin-CHC to individual paxillin-derived LD motifs, we can predict which LD motifs in the paxillin paralogs Hic-5 and leupaxin are likely to be ligands for α-parvin. The sequence alignment in Figure 6 demonstrates that only LD1 is sufficiently conserved in the case of leupaxin, whereas Hic-5 contains three potential α-parvin-binding LD motifs, a hypothesis borne out by experiment (Nikolopoulos and Turner, 2000). Although no interaction of leupaxin with α-parvin has yet been reported, we propose that it will interact with α-parvin via its LD1 motif. Members of the paxillin and parvin families are differentially expressed in human tissues (http://www.hprd.org), and it is possible that they may form tissue-specific complexes.


Structural analysis of the interactions between paxillin LD motifs and alpha-parvin.

Lorenz S, Vakonakis I, Lowe ED, Campbell ID, Noble ME, Hoellerer MK - Structure (2008)

Conservation of α-Parvin Contacting Residues in LD Motifs of Paxillin ParalogsSequence alignment of LD motifs in human paxillin (PAXN), hic-5 (HIC5), and leupaxin (LPXN). Paxillin residues ordered in the crystal structures of the α-parvin-CHC/LD complexes are underlined and those forming contacts with α-parvin-CHC within a radius of 4 Å are boxed.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2572193&req=5

fig6: Conservation of α-Parvin Contacting Residues in LD Motifs of Paxillin ParalogsSequence alignment of LD motifs in human paxillin (PAXN), hic-5 (HIC5), and leupaxin (LPXN). Paxillin residues ordered in the crystal structures of the α-parvin-CHC/LD complexes are underlined and those forming contacts with α-parvin-CHC within a radius of 4 Å are boxed.
Mentions: On the basis of our results for α-parvin, we can make two general predictions with respect to LD recognition by CH domains: First, as noted previously (Wang et al., 2008), we propose that the presence of an N-linker helix is a prerequisite for the interaction with LD motifs. In agreement with this hypothesis, it has been reported that α-actinin, whose canonical CH domains lack this structural element, does not interact with paxillin (Nikolopoulos and Turner, 2000). Since the C-terminal region, including the N-linker helix, is highly conserved throughout the parvin family, we speculate that all parvin paralogs may be able to bind LD motifs. Interestingly, γ-parvin was shown to associate with paxillin in vivo (Yoshimi et al., 2006). Available experiments with β-parvin, however, have proved negative to date (Yamaji et al., 2004), although this protein is more similar in sequence to α-parvin than is γ-parvin (Figure 1C). Second, on the basis of the analysis of differential binding of α-parvin-CHC to individual paxillin-derived LD motifs, we can predict which LD motifs in the paxillin paralogs Hic-5 and leupaxin are likely to be ligands for α-parvin. The sequence alignment in Figure 6 demonstrates that only LD1 is sufficiently conserved in the case of leupaxin, whereas Hic-5 contains three potential α-parvin-binding LD motifs, a hypothesis borne out by experiment (Nikolopoulos and Turner, 2000). Although no interaction of leupaxin with α-parvin has yet been reported, we propose that it will interact with α-parvin via its LD1 motif. Members of the paxillin and parvin families are differentially expressed in human tissues (http://www.hprd.org), and it is possible that they may form tissue-specific complexes.

Bottom Line: Cocrystal structures with these LD motifs reveal the molecular details of their interactions with a common binding site on alpha-parvin-CH(C), which is located at the rim of the canonical fold and includes part of the inter-CH domain linker.Surprisingly, this binding site can accommodate LD motifs in two antiparallel orientations.Taken together, these results reveal an unusual degree of binding degeneracy in the paxillin/alpha-parvin system that may facilitate the assembly of dynamic signaling complexes in the cell.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biophysics, University of Oxford, Oxford OX1 3QU, United Kingdom.

ABSTRACT
The adaptor protein paxillin contains five conserved leucine-rich (LD) motifs that interact with a variety of focal adhesion proteins, such as alpha-parvin. Here, we report the first crystal structure of the C-terminal calponin homology domain (CH(C)) of alpha-parvin at 1.05 A resolution and show that it is able to bind all the LD motifs, with some selectivity for LD1, LD2, and LD4. Cocrystal structures with these LD motifs reveal the molecular details of their interactions with a common binding site on alpha-parvin-CH(C), which is located at the rim of the canonical fold and includes part of the inter-CH domain linker. Surprisingly, this binding site can accommodate LD motifs in two antiparallel orientations. Taken together, these results reveal an unusual degree of binding degeneracy in the paxillin/alpha-parvin system that may facilitate the assembly of dynamic signaling complexes in the cell.

Show MeSH
Related in: MedlinePlus