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Structure and interdomain interactions of a hybrid domain: a disulphide-rich module of the fibrillin/LTBP superfamily of matrix proteins.

Jensen SA, Iqbal S, Lowe ED, Redfield C, Handford PA - Structure (2009)

Bottom Line: Here we present the crystal structure of a fibrillin-1 cbEGF9-hyb2-cbEGF10 fragment, solved to 1.8 A resolution.Pairwise interactions with neighboring cbEGF domains demonstrate extensive interfaces, with the hyb2-cbEGF10 interface dependent on Ca(2+) binding.These observations provide accurate constraints for models of fibrillin organization within the 10-12 nm microfibrils and provide further molecular insights into how Ca(2+) binding influences the intermolecular interactions and biomechanical properties of fibrillin-1.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Oxford, Oxford, UK.

ABSTRACT
The fibrillins and latent transforming growth factor-beta binding proteins (LTBPs) form a superfamily of structurally-related proteins consisting of calcium-binding epidermal growth factor-like (cbEGF) domains interspersed with 8-cysteine-containing transforming growth factor beta-binding protein-like (TB) and hybrid (hyb) domains. Fibrillins are the major components of the extracellular 10-12 nm diameter microfibrils, which mediate a variety of cell-matrix interactions. Here we present the crystal structure of a fibrillin-1 cbEGF9-hyb2-cbEGF10 fragment, solved to 1.8 A resolution. The hybrid domain fold is similar, but not identical, to the TB domain fold seen in previous fibrillin-1 and LTBP-1 fragments. Pairwise interactions with neighboring cbEGF domains demonstrate extensive interfaces, with the hyb2-cbEGF10 interface dependent on Ca(2+) binding. These observations provide accurate constraints for models of fibrillin organization within the 10-12 nm microfibrils and provide further molecular insights into how Ca(2+) binding influences the intermolecular interactions and biomechanical properties of fibrillin-1.

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Alignments of TB, Hybrid, and cbEGF Domains(A–C) TB domains from fibrillin-1 (A), hybrid domains from fibrillin-1 (hyb1 and hyb2) and LTBPs 1-4 (B), and the cbEGF domains found in fibrillin-1 hyb-cbEGF domain pairs and high Ca2+ affinity fibrillin-1 TB-cbEGF pairs (C) were aligned using Clustal W 2.0 (Larkin et al., 2007). Cysteine residues are highlighted in yellow. The positions of the “loop 1” and “X-Gly” interdomain packing sites of the cbEGFs are indicated. Regions that show a high degree of sequence conservation between TB and hyb domains are highlighted in cyan. The Gly-Phe/Tyr dipeptide found at the C-terminal end of the domains, which has previously been shown to be involved in interdomain interactions in TB-cbEGF pairs (Jensen et al., 2005; Lee et al., 2004) and cbEGF-cbEGF pairs (Knott et al., 1996; Smallridge et al., 2003), is highlighted in green.(D) Comparison of the hyb2 domain structure with the structures of cbEGF (green) and TB (blue) domains mirrors the sequence alignment data and confirms the “hybrid” nature of the domain. The conserved Trp at the hydrophobic core of the TB domain is shown as cyan spheres, and the conserved aromatic found at the C-terminal packing site of the cbEGF is shown as green spheres.
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fig5: Alignments of TB, Hybrid, and cbEGF Domains(A–C) TB domains from fibrillin-1 (A), hybrid domains from fibrillin-1 (hyb1 and hyb2) and LTBPs 1-4 (B), and the cbEGF domains found in fibrillin-1 hyb-cbEGF domain pairs and high Ca2+ affinity fibrillin-1 TB-cbEGF pairs (C) were aligned using Clustal W 2.0 (Larkin et al., 2007). Cysteine residues are highlighted in yellow. The positions of the “loop 1” and “X-Gly” interdomain packing sites of the cbEGFs are indicated. Regions that show a high degree of sequence conservation between TB and hyb domains are highlighted in cyan. The Gly-Phe/Tyr dipeptide found at the C-terminal end of the domains, which has previously been shown to be involved in interdomain interactions in TB-cbEGF pairs (Jensen et al., 2005; Lee et al., 2004) and cbEGF-cbEGF pairs (Knott et al., 1996; Smallridge et al., 2003), is highlighted in green.(D) Comparison of the hyb2 domain structure with the structures of cbEGF (green) and TB (blue) domains mirrors the sequence alignment data and confirms the “hybrid” nature of the domain. The conserved Trp at the hydrophobic core of the TB domain is shown as cyan spheres, and the conserved aromatic found at the C-terminal packing site of the cbEGF is shown as green spheres.

Mentions: Early sequencing data for FBN1 cDNA suggested that fibrillin-1 had unique hybrid domains with properties that were similar to both the TB and EGF domains (Corson et al., 1993; Pereira et al., 1993). An alignment of various TB and cbEGF domains from fibrillin-1 with the hybrid domains of fibrillin-1 and the LTBPs (Figures 5A–5C) shows these similarities. The fibrillin and LTBP hybrid domain sequences share several conserved features including the positions of 8 cysteine residues, a conserved aromatic residue at the N terminus of the domain, a central Gly-x-x-Trp-Gly sequence, and a Gly-Phe/Tyr dipeptide at the C terminus. A comparison of the hybrid domains with the TB domains of fibrillin-1 shows that they share similar features at their N-terminal ends, with the exception of the Cys-Cys-Cys sequence in the TB domain being replaced with a Cys-Cys dipeptide in the hyb domains.


Structure and interdomain interactions of a hybrid domain: a disulphide-rich module of the fibrillin/LTBP superfamily of matrix proteins.

Jensen SA, Iqbal S, Lowe ED, Redfield C, Handford PA - Structure (2009)

Alignments of TB, Hybrid, and cbEGF Domains(A–C) TB domains from fibrillin-1 (A), hybrid domains from fibrillin-1 (hyb1 and hyb2) and LTBPs 1-4 (B), and the cbEGF domains found in fibrillin-1 hyb-cbEGF domain pairs and high Ca2+ affinity fibrillin-1 TB-cbEGF pairs (C) were aligned using Clustal W 2.0 (Larkin et al., 2007). Cysteine residues are highlighted in yellow. The positions of the “loop 1” and “X-Gly” interdomain packing sites of the cbEGFs are indicated. Regions that show a high degree of sequence conservation between TB and hyb domains are highlighted in cyan. The Gly-Phe/Tyr dipeptide found at the C-terminal end of the domains, which has previously been shown to be involved in interdomain interactions in TB-cbEGF pairs (Jensen et al., 2005; Lee et al., 2004) and cbEGF-cbEGF pairs (Knott et al., 1996; Smallridge et al., 2003), is highlighted in green.(D) Comparison of the hyb2 domain structure with the structures of cbEGF (green) and TB (blue) domains mirrors the sequence alignment data and confirms the “hybrid” nature of the domain. The conserved Trp at the hydrophobic core of the TB domain is shown as cyan spheres, and the conserved aromatic found at the C-terminal packing site of the cbEGF is shown as green spheres.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC2724076&req=5

fig5: Alignments of TB, Hybrid, and cbEGF Domains(A–C) TB domains from fibrillin-1 (A), hybrid domains from fibrillin-1 (hyb1 and hyb2) and LTBPs 1-4 (B), and the cbEGF domains found in fibrillin-1 hyb-cbEGF domain pairs and high Ca2+ affinity fibrillin-1 TB-cbEGF pairs (C) were aligned using Clustal W 2.0 (Larkin et al., 2007). Cysteine residues are highlighted in yellow. The positions of the “loop 1” and “X-Gly” interdomain packing sites of the cbEGFs are indicated. Regions that show a high degree of sequence conservation between TB and hyb domains are highlighted in cyan. The Gly-Phe/Tyr dipeptide found at the C-terminal end of the domains, which has previously been shown to be involved in interdomain interactions in TB-cbEGF pairs (Jensen et al., 2005; Lee et al., 2004) and cbEGF-cbEGF pairs (Knott et al., 1996; Smallridge et al., 2003), is highlighted in green.(D) Comparison of the hyb2 domain structure with the structures of cbEGF (green) and TB (blue) domains mirrors the sequence alignment data and confirms the “hybrid” nature of the domain. The conserved Trp at the hydrophobic core of the TB domain is shown as cyan spheres, and the conserved aromatic found at the C-terminal packing site of the cbEGF is shown as green spheres.
Mentions: Early sequencing data for FBN1 cDNA suggested that fibrillin-1 had unique hybrid domains with properties that were similar to both the TB and EGF domains (Corson et al., 1993; Pereira et al., 1993). An alignment of various TB and cbEGF domains from fibrillin-1 with the hybrid domains of fibrillin-1 and the LTBPs (Figures 5A–5C) shows these similarities. The fibrillin and LTBP hybrid domain sequences share several conserved features including the positions of 8 cysteine residues, a conserved aromatic residue at the N terminus of the domain, a central Gly-x-x-Trp-Gly sequence, and a Gly-Phe/Tyr dipeptide at the C terminus. A comparison of the hybrid domains with the TB domains of fibrillin-1 shows that they share similar features at their N-terminal ends, with the exception of the Cys-Cys-Cys sequence in the TB domain being replaced with a Cys-Cys dipeptide in the hyb domains.

Bottom Line: Here we present the crystal structure of a fibrillin-1 cbEGF9-hyb2-cbEGF10 fragment, solved to 1.8 A resolution.Pairwise interactions with neighboring cbEGF domains demonstrate extensive interfaces, with the hyb2-cbEGF10 interface dependent on Ca(2+) binding.These observations provide accurate constraints for models of fibrillin organization within the 10-12 nm microfibrils and provide further molecular insights into how Ca(2+) binding influences the intermolecular interactions and biomechanical properties of fibrillin-1.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Oxford, Oxford, UK.

ABSTRACT
The fibrillins and latent transforming growth factor-beta binding proteins (LTBPs) form a superfamily of structurally-related proteins consisting of calcium-binding epidermal growth factor-like (cbEGF) domains interspersed with 8-cysteine-containing transforming growth factor beta-binding protein-like (TB) and hybrid (hyb) domains. Fibrillins are the major components of the extracellular 10-12 nm diameter microfibrils, which mediate a variety of cell-matrix interactions. Here we present the crystal structure of a fibrillin-1 cbEGF9-hyb2-cbEGF10 fragment, solved to 1.8 A resolution. The hybrid domain fold is similar, but not identical, to the TB domain fold seen in previous fibrillin-1 and LTBP-1 fragments. Pairwise interactions with neighboring cbEGF domains demonstrate extensive interfaces, with the hyb2-cbEGF10 interface dependent on Ca(2+) binding. These observations provide accurate constraints for models of fibrillin organization within the 10-12 nm microfibrils and provide further molecular insights into how Ca(2+) binding influences the intermolecular interactions and biomechanical properties of fibrillin-1.

Show MeSH
Related in: MedlinePlus