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3 Acta Biochimica Polonica

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Supramolecularity creates nonstandard protein ligands

100%

Piekarska B. , Rybarska J. , Stopa B. , Zemanek G. , Król M. , Roterman I. , Konieczny L.

Acta Biochimica Polonica

1999

tom 46

nr 4

841-851

Congo red and a group of structurally related dyes long used to stain amyloid proteins are known to associate in water solutions. The self-association of some dyes belonging to this group appears particularly strong. In water solutions their molecules are arranged in ribbon-like micellar forms with liquid crystalline properties. These compounds have recently been found to form complexeswith some native proteins in a non-standard way. Gaps formed by the local distribution of β-sheets in proteins probably represent the receptor sites for these dye ligands. They may result from higher structural instability in unfolding conditions, but also may appear as long range cooperative fluctuations generated by ligand binding. Immunoglobulins G were chosen as model binding proteins to check the mechanism of binding of these dyes. The sites of structural changes generated by antigen binding in antibodies, believed to act as a signal propagated to distant parts of the molecule, were assumed to be suitable sites for the complexation of liquid-crystalline dyes. This assumption was confirmed by proving that antibodies engaged in immune complexation really do bind these dyes; as expected, this binding affects their function by significantly enhancing antigen binding and simultaneously inhibiting C1q attachment. Binding of these supramolecular dyes by some other native proteins including serpins and their natural complexes was also shown. The strict dependence of the ligation properties on strong self-assembling and the particular arrangement of dye molecules indicate that supramolecularity is the feature that creates non-standard protein ligands, with potential uses in medicine and experimental science.

The structure and protein binding of amyloid-specific dye reagents.

88%

Stopa B. , Piekarska B. , Konieczny L. , Rybarska J. , Spólnik P. , Zemanek G. , Roterman I. , Król M.

Acta Biochimica Polonica

2003

tom 50

nr 4

1213-1227

The self-assembling tendency and protein complexation capability of dyes related to Congo red and also some dyes of different structure were compared to explain the mechanism of Congo red binding and the reason for its specific affinity for β-structure. Complexation with proteins was measured directly and expressed as the number of dye molecules bound to heat-aggregated IgG and to two light chains with different structural stability. Binding of dyes to rabbit antibodies was measured indirectly as the enhancement effect of the dye on immune complex formation. Self-assembling was tested using dynamic light scattering to measure the size of the supramolecular assemblies. In general the results show that the supramolecular form of a dye is the main factor determining its complexation capability. Dyes that in their compact supramolecular organization are ribbon-shaped may adhere to polypeptides of β-conformation due to the architectural compatibility in this unique structural form. The optimal fit in complexation seems to depend on two contradictory factors involving, on the one hand, the compactness of the non-covalently stabilized supramolecular ligand, and the dynamic character producing its plasticity on the other. As a result, the highest protein binding capability is shown by dyes with a moderate self-assembling tendency, while those arranging into either very rigid or very unstable supramolecular entities are less able to bind.

The structure and protein binding of amyloid-specific dye reagents

75%

Stopa B. , Piekarska B. , Konieczny L. , Rybarska J. , Spolnik P. , Zemanek G. , Roterman I. , Krol M.

Acta Biochimica Polonica

2003

tom 50

nr 4

The self-assembling tendency and protein complexation capability of dyes related to Congo red and also some dyes of different structure were compared to explain the mechanism of Congo red binding and the reason for its specific affinity for /3-struc- ture. Complexation with proteins was measured directly and expressed as the number of dye molecules bound to heat-aggregated IgG and to two light chains with different structural stability. Binding of dyes to rabbit antibodies was measured indirectly as the enhancement effect of the dye on immune complex formation. Self-assembling was tested using dynamic light scattering to measure the size of the supra- molecular assemblies. In general the results show that the supramolecular form of a dye is the main factor determining its complexation capability. Dyes that in their compact supramolecular organization are ribbon-shaped may adhere to polypeptides of /3-conformation due to the architectural compatibility in this unique structural form. The optimal fit in complexation seems to depend on two contradictory factors involving, on the one hand, the compactness of the non-covalently stabilized supra- molecular ligand, and the dynamic character producing its plasticity on the other. As a result, the highest protein binding capability is shown by dyes with a moderate self-assembling tendency, while those arranging into either very rigid or very unstable supramolecular entities are less able to bind.