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Force-induced remodelling of proteins and their complexes.

Chen Y, Radford SE, Brockwell DJ - Curr. Opin. Struct. Biol. (2015)

Bottom Line: The effects of force on the biophysical properties of biological systems can be large and varied.As these effects are only apparent in the presence of force, studies on the same proteins using traditional ensemble biophysical methods can yield apparently conflicting results.Where appropriate, therefore, force measurements should be integrated with other experimental approaches to understand the physiological context of the system under study.

View Article: PubMed Central - PubMed

Affiliation: Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.

No MeSH data available.


Related in: MedlinePlus

The structures of force-resistant and force-sensitive protein complexes. (a) in the absence of force, the N-terminal strand of FLNa20 (green, left) occludes the binding site for the integrin β-cytoplasmic tail (grey, right) on FLNa21 (red). (b) The bacterial Fim pilus is assembled by a donor strand complementation mechanism, whereby the Immunoglobulin-like fold of one domain (FimG in this case, red) missing the C-terminal β-strand is completed by the binding of an N-terminal extension of the subsequent Ig-like domain (FimF, grey). (c) and (d) upon mechanical extension, the cryptic vinculin binding sites (VBS, blue) within α-catenin ((c), red) and talin ((d), red) become accessible, triggering vinculin binding to the VBS (green and blue in the inset structures, respectively). (e) the complex formed between the C-terminal domain of TonB (red), tethered to the inner membrane of Gram negative bacteria and the TonB box (grey) of the outer membrane protein BtuB, that together span the periplasm. Structures drawn using UCSF Chimera [97] and PDB files:2J3S [98], 2BRQ [99], 2GSK [58], 3JWN [100], 4IGG [101], 4EHP [102], 1XWX (note that this is a theoretical model) [103] and 1 U6H [103].
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Figure 3: The structures of force-resistant and force-sensitive protein complexes. (a) in the absence of force, the N-terminal strand of FLNa20 (green, left) occludes the binding site for the integrin β-cytoplasmic tail (grey, right) on FLNa21 (red). (b) The bacterial Fim pilus is assembled by a donor strand complementation mechanism, whereby the Immunoglobulin-like fold of one domain (FimG in this case, red) missing the C-terminal β-strand is completed by the binding of an N-terminal extension of the subsequent Ig-like domain (FimF, grey). (c) and (d) upon mechanical extension, the cryptic vinculin binding sites (VBS, blue) within α-catenin ((c), red) and talin ((d), red) become accessible, triggering vinculin binding to the VBS (green and blue in the inset structures, respectively). (e) the complex formed between the C-terminal domain of TonB (red), tethered to the inner membrane of Gram negative bacteria and the TonB box (grey) of the outer membrane protein BtuB, that together span the periplasm. Structures drawn using UCSF Chimera [97] and PDB files:2J3S [98], 2BRQ [99], 2GSK [58], 3JWN [100], 4IGG [101], 4EHP [102], 1XWX (note that this is a theoretical model) [103] and 1 U6H [103].

Mentions: At a longer length-scale force can induce conformational re-arrangements leading to allosteric activation or inhibition of a protein or protein complex. One notable case is titin which, in addition to its structural role, can act as a strain sensor, triggering muscle adaptation upon detection of mechanical strain. At physiologically relevant forces, low enough to maintain titin’s structural domains in the folded state (<50 pN), the C-terminal kinase domain unfolds via a multistep pathway. Early in the unfolding process the C-terminal tail of the kinase domain unravels from the remainder of the protein. Extension in this way activates the kinase by both allowing access of ATP to its binding site (which in the absence of force is occluded by the C-terminus) and by triggering autophosphorylation of a tyrosine residue that inhibits activity [35]. Force is also integral to outside-in and inside-out signal transduction between cells and their surroundings. Transmembrane proteins such as integrins are vital to this network, linking the extra-cellular matrix with the actin cytoskeleton. Many adaptor proteins are involved in this signal transduction pathway, with filamin playing a central role [36]. At the molecular level, filamin complex formation is driven by a β-strand augmentation of the 21st immunoglobulin-like domain of filamin A (FLNa21) by the β-integrin tail (Figure 3a). Under no force, FLNa21 cannot bind to integrin due to occlusion of the binding site by the N-terminal β-strand of the preceding filamin domain (Figure 3a). Rognoni et al. [37] investigated the mechanical behaviour of the auto-inhibited state and showed that the force-dependent gating characteristics of filamin allow for a cellular response to surprisingly low forces (the affinity for the C-terminal tail peptides of different interaction partners is increased up to seventeen fold upon increasing applied force from to 2 to 5 pN). The same authors then showed that switching between the auto-inhibited and activated state is enabled by cis–trans isomerisation of a proline residue in the force sensing domain (FLNa20), weakening the stability of the auto-inhibited state. Whilst cis–trans isomerisation does result in bond lengthening, the authors suggest that force induced unfolding accelerates this isomerisation, rather than force driving isomerisation per se [38•].


Force-induced remodelling of proteins and their complexes.

Chen Y, Radford SE, Brockwell DJ - Curr. Opin. Struct. Biol. (2015)

The structures of force-resistant and force-sensitive protein complexes. (a) in the absence of force, the N-terminal strand of FLNa20 (green, left) occludes the binding site for the integrin β-cytoplasmic tail (grey, right) on FLNa21 (red). (b) The bacterial Fim pilus is assembled by a donor strand complementation mechanism, whereby the Immunoglobulin-like fold of one domain (FimG in this case, red) missing the C-terminal β-strand is completed by the binding of an N-terminal extension of the subsequent Ig-like domain (FimF, grey). (c) and (d) upon mechanical extension, the cryptic vinculin binding sites (VBS, blue) within α-catenin ((c), red) and talin ((d), red) become accessible, triggering vinculin binding to the VBS (green and blue in the inset structures, respectively). (e) the complex formed between the C-terminal domain of TonB (red), tethered to the inner membrane of Gram negative bacteria and the TonB box (grey) of the outer membrane protein BtuB, that together span the periplasm. Structures drawn using UCSF Chimera [97] and PDB files:2J3S [98], 2BRQ [99], 2GSK [58], 3JWN [100], 4IGG [101], 4EHP [102], 1XWX (note that this is a theoretical model) [103] and 1 U6H [103].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4499843&req=5

Figure 3: The structures of force-resistant and force-sensitive protein complexes. (a) in the absence of force, the N-terminal strand of FLNa20 (green, left) occludes the binding site for the integrin β-cytoplasmic tail (grey, right) on FLNa21 (red). (b) The bacterial Fim pilus is assembled by a donor strand complementation mechanism, whereby the Immunoglobulin-like fold of one domain (FimG in this case, red) missing the C-terminal β-strand is completed by the binding of an N-terminal extension of the subsequent Ig-like domain (FimF, grey). (c) and (d) upon mechanical extension, the cryptic vinculin binding sites (VBS, blue) within α-catenin ((c), red) and talin ((d), red) become accessible, triggering vinculin binding to the VBS (green and blue in the inset structures, respectively). (e) the complex formed between the C-terminal domain of TonB (red), tethered to the inner membrane of Gram negative bacteria and the TonB box (grey) of the outer membrane protein BtuB, that together span the periplasm. Structures drawn using UCSF Chimera [97] and PDB files:2J3S [98], 2BRQ [99], 2GSK [58], 3JWN [100], 4IGG [101], 4EHP [102], 1XWX (note that this is a theoretical model) [103] and 1 U6H [103].
Mentions: At a longer length-scale force can induce conformational re-arrangements leading to allosteric activation or inhibition of a protein or protein complex. One notable case is titin which, in addition to its structural role, can act as a strain sensor, triggering muscle adaptation upon detection of mechanical strain. At physiologically relevant forces, low enough to maintain titin’s structural domains in the folded state (<50 pN), the C-terminal kinase domain unfolds via a multistep pathway. Early in the unfolding process the C-terminal tail of the kinase domain unravels from the remainder of the protein. Extension in this way activates the kinase by both allowing access of ATP to its binding site (which in the absence of force is occluded by the C-terminus) and by triggering autophosphorylation of a tyrosine residue that inhibits activity [35]. Force is also integral to outside-in and inside-out signal transduction between cells and their surroundings. Transmembrane proteins such as integrins are vital to this network, linking the extra-cellular matrix with the actin cytoskeleton. Many adaptor proteins are involved in this signal transduction pathway, with filamin playing a central role [36]. At the molecular level, filamin complex formation is driven by a β-strand augmentation of the 21st immunoglobulin-like domain of filamin A (FLNa21) by the β-integrin tail (Figure 3a). Under no force, FLNa21 cannot bind to integrin due to occlusion of the binding site by the N-terminal β-strand of the preceding filamin domain (Figure 3a). Rognoni et al. [37] investigated the mechanical behaviour of the auto-inhibited state and showed that the force-dependent gating characteristics of filamin allow for a cellular response to surprisingly low forces (the affinity for the C-terminal tail peptides of different interaction partners is increased up to seventeen fold upon increasing applied force from to 2 to 5 pN). The same authors then showed that switching between the auto-inhibited and activated state is enabled by cis–trans isomerisation of a proline residue in the force sensing domain (FLNa20), weakening the stability of the auto-inhibited state. Whilst cis–trans isomerisation does result in bond lengthening, the authors suggest that force induced unfolding accelerates this isomerisation, rather than force driving isomerisation per se [38•].

Bottom Line: The effects of force on the biophysical properties of biological systems can be large and varied.As these effects are only apparent in the presence of force, studies on the same proteins using traditional ensemble biophysical methods can yield apparently conflicting results.Where appropriate, therefore, force measurements should be integrated with other experimental approaches to understand the physiological context of the system under study.

View Article: PubMed Central - PubMed

Affiliation: Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK; School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.

No MeSH data available.


Related in: MedlinePlus