| 1. |
- Boyle, Aimee L., et al.
(författare)
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Squaring the Circle in Peptide Assembly: From Fibers to Discrete Nanostructures by de Novo Design
- 2012
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 134:37, s. 15457-15467
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Tidskriftsartikel (refereegranskat)abstract
- The design of bioinspired nanostructures and materials of defined size and shape is challenging as it pushes our understanding of biomolecular assembly to its limits. In such endeavors, DNA is the current building block of choice because of its predictable and programmable self-assembly. The use of peptide- and protein-based systems, however, has potential advantages due to their more-varied chemistries, structures and functions, and the prospects for recombinant production through gene synthesis and expression. Here, we present the design and characterization of two complementary peptides programmed to form a parallel heterodimeric coiled coil, which we use as the building blocks for larger, supramolecular assemblies. To achieve the latter, the two peptides are joined via peptidic linkers of variable lengths to produce a range of assemblies, from flexible fibers of indefinite length, through large colloidal-scale assemblies, down to closed and discrete nanoscale objects of defined stoichiometry. We posit that the different modes of assembly reflect the interplay between steric constraints imposed by short linkers and the bulk of the helices, and entropic factors that favor the formation of many smaller objects as the linker length is increased. This approach, and the resulting linear and proteinogenic polypeptides, represents a new route for constructing complex peptide-based assemblies and biomaterials.
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| 2. |
- Kuwada, Nathan J., et al.
(författare)
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Tuning the performance of an artificial protein motor
- 2011
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 84:3
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Tidskriftsartikel (refereegranskat)abstract
- The Tumbleweed (TW) is a concept for an artificial, tri-pedal, protein-based motor designed to move unidirectionally along a linear track by a diffusive tumbling motion. Artificial motors offer the unique opportunity to explore how motor performance depends on design details in a way that is open to experimental investigation. Prior studies have shown that TW's ability to complete many successive steps can be critically dependent on the motor's diffusional step time. Here, we present a simulation study targeted at determining how to minimize the diffusional step time of the TW motor as a function of two particular design choices: nonspecific motor-track interactions and molecular flexibility. We determine an optimal nonspecific interaction strength and establish a set of criteria for optimal molecular flexibility as a function of the nonspecific interaction. We discuss our results in the context of similarities to biological, linear stepping diffusive molecular motors with the aim of identifying general engineering principles for protein motors.
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| 3. |
- Small, Lara S.R., et al.
(författare)
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The bar-hinge motor : A synthetic protein design exploiting conformational switching to achieve directional motility
- 2019
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- One challenge to synthetic biology is to design functional machines from natural building blocks, from individual amino acids up to larger motifs such as the coiled coil. Here we investigate a novel bipedal motor concept, the Bar-Hinge Motor (BHM), a peptide-based motor capable of executing directed motion via externally controlled conformational switching between a straight bar and a V-shaped hinged form. Incorporating ligand-regulated binding to a DNA track and periodic control of ligand supply makes the BHM an example of a 'clocked walker'. Here, we employ a coarse-grained computational model for the BHM to assess the feasibility of a proposed experimental realization, with conformational switching regulated through the photoisomerization of peptide-bound azobenzene molecules. The results of numerical simulations using the model show that the incorporation of this conformational switch is necessary for the BHM to execute directional, rather than random, motion on a one-dimensional track. The power-stroke-driven directed motion is seen in the model even under conditions that underestimate the level of control we expect to be able to produce in the experimental realisation, demonstrating that this type of design should be an excellent vehicle for exploring the physics behind protein motion. By investigating its force-dependent dynamics, we show that the BHM is capable of directional motion against an applied load, even in the more relaxed conformational switching regimes. Thus, BHM appears to be an excellent candidate for a motor design incorporating a power stroke, enabling us to explore the ability of switchable coiled-coil designs to deliver power strokes within synthetic biology.
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| 4. |
- Spring, Frances A., et al.
(författare)
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Intercellular adhesion molecule-4 binds alpha(4)beta(1) and alpha(V)-family integrins through novel integrin-binding mechanisms
- 2001
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Ingår i: Blood. - 1528-0020. ; 98:2, s. 458-466
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Tidskriftsartikel (refereegranskat)abstract
- The LW blood group glycoprotein, ICAM-4, is a member of the intercellular adhesion molecule (ICAM) family expressed in erythroid cells. To begin to address the function of this molecule, ligands for ICAM-4 on hemopoietic and nonhemopoietic cell lines were identified. Peptide inhibition studies suggest that adhesion of cell lines to an ICAM-4-Fc construct is mediated by an LDV-inhibitable integrin on hemopoietic cells and an RGD-inhibitable integrin on nonhemopoietic cells. Antibody inhibition studies identified the hemopoietic integrin as alpha(4)beta(1.) Antibody inhibition studies on alpha(4)beta(1)-negative, nonhemopoietic cell lines suggested that adhesion of these cells is mediated by alpha(V) integrins (notably alpha(V)beta(1) and alpha(V)beta(5)). The structure of ICAM-4 modeled on the crystal structure of ICAM-2 was used to identify surface-exposed amino acid residues for site-directed mutagenesis. Neither an unusual LETS nor an LDV motif in the first domain of ICAM-4 was critical for integrin binding. ICAM-4 is the first ICAM family member shown to be a ligand for integrins other than those of the beta(2) family, and the data suggest that ICAM-4 has a novel integrin-binding site(s). These findings suggest a role for ICAM-4 in normal erythropoiesis and may also be relevant to the adhesive interactions of sickle cells.
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| 5. |
- van Weering, Jan R. T., et al.
(författare)
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Molecular basis for SNX-BAR-mediated assembly of distinct endosomal sorting tubules
- 2012
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Ingår i: EMBO Journal. - : Wiley. - 0261-4189 .- 1460-2075. ; 31:23, s. 4466-4480
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Tidskriftsartikel (refereegranskat)abstract
- Sorting nexins (SNXs) are regulators of endosomal sorting. For the SNX-BAR subgroup, a Bin/Amphiphysin/Rvs (BAR) domain is vital for formation/stabilization of tubular subdomains that mediate cargo recycling. Here, by analysing the in vitro membrane remodelling properties of all 12 human SNX-BARs, we report that some, but not all, can elicit the formation of tubules with diameters that resemble sorting tubules observed in cells. We reveal that SNX-BARs display a restricted pattern of BAR domain-mediated dimerization, and by resolving a 2.8 angstrom structure of a SNX1-BAR domain homodimer, establish that dimerization is achieved in part through neutralization of charged residues in the hydrophobic BAR-dimerization interface. Membrane remodelling also requires functional amphipathic helices, predicted to be present in all SNX-BARs, and the formation of high order SNX-BAR oligomers through selective 'tip-loop' interactions. Overall, the restricted and selective nature of these interactions provide a molecular explanation for how distinct SNX-BAR-decorated tubules are nucleated from the same endosomal vacuole, as observed in living cells. Our data provide insight into the molecular mechanism that generates and organizes the tubular endosomal network.
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