Elastomeric proteins: biological roles, structures and mechanisms (original) (raw)

Mechanisms of elasticity in elastic proteins

2012

This thesis investigates the mechanical properties of the elastic proteins isolated by cyanogen bromide digestion from lamprey cartilages and compares them with the mammalian protein, elastin. Thermomechanical testing and measurements of the e ects of hydrophobic solvents on mechanics are used to determine the energetic and entropic contributions to the mechanical properties and the role of solvent interactions. Raman microspectrometry is shown to be a valuable tool in determining the secondary structure of the proteins, their interactions with water and molecular-level e ects of mechanical strain. The supramolecular structure of the proteins matrices are investigated using nonlinear microscopy and X-ray di raction. The mechanical properties of brous elastin agreed with those previously reported with elastic moduli in the region of 0.2-0.4 MPa. Elastic moduli decrease by approximately 25% with increased temperature, which was accompanied by a small decrease in hysteresis loss. In ag...

Wheat seed proteins exhibit a complex mechanism of protein elasticity

Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 2001

Elastomeric proteins are found in a number of animal tissues (elastin, abductin and resilin), where they have evolved to fulfil a range of biological functions. All exhibit rubber-like elasticity, undergoing deformation without rupture, storing the energy involved in deformation, and then recovering to their initial state when the stress is removed. The second part of the process is passive, entropy decreasing when the proteins are deformed, with the higher entropy of the relaxed state providing the driving force for recoil. In plants there is only one well-documented elastomeric protein system, the alcohol-soluble seed storage proteins (gluten) of wheat. The elastic properties of these proteins have no known biological role, the proteins acting as a store for the germinating seed. Here we show that the modulus of elasticity of a group of wheat gluten subunits, when cross-linked by gamma-radiation, is similar to that of the cross-linked polypentapeptide of elastin. However, thermoelasticity studies indicate that the mechanism of elastic recoil is different from elastin and other characterized protein elastomers. Elastomeric force, f, has two components, an internal energy component, f(e), and an entropic component, f(s). The ratio f(e)/f can be determined experimentally; if this ratio is less than 0.5 the elastomeric force is predominantly entropic in origin. The ratio was determined as 5.6 for the cross-linked high M(r) subunits of wheat glutenin and near zero for the cross-linked polypentapeptide of elastin. Tensile stress must be entropic or energetic in origin, the results would suggest that elastic recoil in the wheat gluten subunits, in part, may be associated with extensive hydrogen bonding within and between subunits and that entropic and energetic mechanisms contribute to the observed elasticity.

1999 Biochimie the struct elastin and functions

Elastin structures and their significance towards elastic recoil properties have been reviewed. Starting from the initial hypothesis that elastin conformation is conditioned by that of its monomer, the structure of tropoelastin was first described using theoretical and experimental methods and a [3 class folding type was evidenced for the isolated unbound tropoelastin molecules. The structure of elastin in the solid state was consistent with that of its monomer and consequently, fibrous elastin appeared constituted of globular tropoelastin molecules. Finally, theoretical and experimental considerations have led us to the conclusion that the functional form of the elastomer, water swollen elastin, could be a triphasic system comprising the protein chains, hydration water and solvent water. Following this description, the dynamic structural equilibria occurring within elastin hydrophobic domains and the plastisizing effect of water could explain elastin elasticity, in keeping with a classical entropic mechanism. © 1999 Soci6t6 frangaise de biochimie et biologie mol6culaire / Editions scientifiques et m6dicales Elsevier SAS elastin / secondary structures / elasticity

Wheat gluten elasticity: a similar molecular basis to elastin?

FEBS Letters, 1984

We have used circular dichroism spectroscopy and structure prediction to study the secondary structure of a group of gluten proteins. They have short a-helices at the N-and C-termini, which are cross-linked by disulphide bonds. The long repetitive central domain has regular p-turns. This structure is similar to that previously proposed for elastin, suggesting a common molecular basis for elasticity.

Mechanical Properties of Intermediate Filament Proteins

Methods in Enzymology, 2016

Purified intermediate filament proteins can be reassembled in vitro to produce polymers closely resembling those found in cells, and these filament form viscoelastic gels. The crosslinks holding IFs together in the network include specific bonds between polypeptides extending from the filament surface and ionic interactions mediated by divalent cations. IF networks exhibit striking non-linear elasticity with stiffness, as quantified by shear modulus, increasing an order of magnitude as the networks are deformed to large stains resembling those that soft tissues undergo in vivo. Individual Ifs can be stretched to more than 2 or 3 times their resting length without breaking. At least ten different rheometric methods have been used to quantify the viscoelasticity of IF networks over a wide range of timescales and strain magnitudes. The mechanical roles of different classes of IF on mesenchymal and epithelial cells in culture have also been studied by an even wider range of microrheological methods. These studies have documented the effects on cell mechanics when IFs are genetically or pharmacologically disrupted or when normal or mutant IF proteins are exogenously expressed in cells. Consistent with in vitro rheology, the mechanical role of IFs is more apparent as cells are subjected to larger and more frequent deformations.