Kannatanu õiguste mõju üldmenetluse võistlevusele

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Masintõlkimise autoriõiguslikke küsimusi

http://tartu.ester.ee/record=b2654659~S1*es

Interaction of β-Sheet Folds with a Gold Surface

The adsorption of proteins on inorganic surfaces is of fundamental biological importance. Further, biomedical and nanotechnological applications increasingly use interfaces between inorganic material and polypeptides. Yet, the underlying adsorption mechanism of polypeptides on surfaces is not well understood and experimentally difficult to analyze. Therefore, we investigate here the interactions of polypeptides with a gold(111) surface using computational molecular dynamics (MD) simulations with a polarizable gold model in explicit water. Our focus in this paper is the investigation of the interaction of polypeptides with β-sheet folds. First, we concentrate on a β-sheet forming model peptide. Second, we investigate the interactions of two domains with high β-sheet content of the biologically important extracellular matrix protein fibronectin (FN). We find that adsorption occurs in a stepwise mechanism both for the model peptide and the protein. The positively charged amino acid Arg facilitates the initial contact formation between protein and gold surface. Our results suggest that an effective gold-binding surface patch is overall uncharged, but contains Arg for contact initiation. The polypeptides do not unfold on the gold surface within the simulation time. However, for the two FN domains, the relative domain-domain orientation changes. The observation of a very fast and strong adsorption indicates that in a biological matrix, no bare gold surfaces will be present. Hence, the bioactivity of gold surfaces (like bare gold nanoparticles) will critically depend on the history of particle administration and the proteins present during initial contact between gold and biological material. Further, gold particles may act as seeds for protein aggregation. Structural re-organization and protein aggregation are potentially of immunological importance

Plasma and cellular fibronectin: distinct and independent functions during tissue repair

Fibronectin (FN) is a ubiquitous extracellular matrix (ECM) glycoprotein that plays vital roles during tissue repair. The plasma form of FN circulates in the blood, and upon tissue injury, is incorporated into fibrin clots to exert effects on platelet function and to mediate hemostasis. Cellular FN is then synthesized and assembled by cells as they migrate into the clot to reconstitute damaged tissue. The assembly of FN into a complex three-dimensional matrix during physiological repair plays a key role not only as a structural scaffold, but also as a regulator of cell function during this stage of tissue repair. FN fibrillogenesis is a complex, stepwise process that is strictly regulated by a multitude of factors. During fibrosis, there is excessive deposition of ECM, of which FN is one of the major components. Aberrant FN-matrix assembly is a major contributing factor to the switch from normal tissue repair to misregulated fibrosis. Understanding the mechanisms involved in FN assembly and how these interplay with cellular, fibrotic and immune responses may reveal targets for the future development of therapies to regulate aberrant tissue-repair processes

Synergistic activity of the ninth and tenth FIII domains of human fibronectin depends upon structural stability.

The ninth and tenth FIII domains (FIII9-10) of human fibronectin act in synergy to promote cell adhesion via the interaction with integrin receptors. Here we describe the functional and structural properties of a set of recombinant FIII9-10 mutants containing various alanine substitutions within the key synergistic site, DRVPHSRN in FIII9, either alone or in combination with another substitution (Leu(1408) to Pro), on the opposite face of FIII9, that increases stability and the functional capacity of FIII9-10. We show that the introduction of mutations into the synergistic sequence of FIII9-10 has a negative effect on the adhesion of baby hamster kidney fibroblasts and results in reduced ability of these ligands to recognize integrin alpha(5)beta(1). Conformational stability of the FIII9 domain in the synergy site mutants is likewise reduced in comparison with native FIII9. The Leu(1408) to Pro substitution in mutant FIII9-10 proteins carrying substitutions in the synergy site results in a substantial recovery of the adhesive activity of the mutants and affinity to alpha(5)beta(1). In keeping with the enhancement of functional activity, the Leu(1408) to Pro substitution in the FIII9-10 synergy site mutants also causes a significant increase in conformational stability of FIII9. These observations imply a strong positive correlation between the biological activity and conformational stability of the assessed FIII9-10 mutants and suggest that a Leu(1408) to Pro substitution restores the biological activity of the mutants via their ability to restore their conformational stability. We conclude that domain stability may be a major determinant of the synergistic potential of FIII9. Our data underscore the value of using more than one approach in such structure-function studies and the requirement for validating the global structural integrity of protein ligands in which sequences that disrupt function have been perturbed

Interdomain tilt angle determines integrin-dependent function of the ninth and tenth FIII domains of human fibronectin

Integrins are an important family of signaling receptors that mediate diverse cellular processes. The binding of the abundant extracellular matrix ligand fibronectin to integrins 51 and v3 is known to depend upon the Arg-Gly-Asp (RGD) motif on the tenth fibronectin FIII domain. The adjacent ninth FIII domain provides a synergistic effect on RGD-mediated integrin 51 binding and downstream function. The precise molecular basis of this synergy remains elusive. Here we have dissected further the function of FIII9 in integrin binding by analyzing the biological activity of the FIII9-10 interdomain interface variants and by determining their structural and dynamic properties in solution. We demonstrate that the contribution of FIII9 to both 51 and v3 binding and downstream function critically depends upon the interdomain tilt between the FIII9 and FIII10 domains. Our data suggest that modulation of integrin binding by FIII9 may arise in part from its steric properties that determine accessibility of the RGD motif. These findings have wider implications for mechanisms of integrin-ligand binding in the physiological context