Supramolecular ligands: Monomer structure and protein ligation capability

Stopa, Barbara; Górny, Magdalena; Konieczny, Leszek; Piekarska, Barbara; Rybarska, Janina; Skowronek, Marek; Roterman, Irena

doi:10.1016/s0300-9084(99)80001-7

Cited by 48 publications

(45 citation statements)

References 17 publications

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“…The interaction of Congo red with protein molecules may involve a complex of multiple protein molecules with intercalated Congo red molecules. Intercalation as a mechanism of binding of Congo red molecules between peptide chains has also been suggested by Stopa and co-workers (38).…”

Section: Amyloid Fibrils and Native Conformations Show Differentmentioning

confidence: 68%

Is Congo Red an Amyloid-specific Dye?

Khurana

Uversky

Nielsen

et al. 2001

Journal of Biological Chemistry

295

238

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Congo red (CR) binding, monitored by characteristic yellow-green birefringence under crossed polarization has been used as a diagnostic test for the presence of amyloid in tissue sections for several decades. This assay is also widely used for the characterization of in vitro amyloid fibrils. In order to probe the structural specificity of Congo red binding to amyloid fibrils we have used an induced circular dichroism (CD) assay. Amyloid fibrils from insulin and the variable domain of Ig light chain demonstrate induced CD spectra upon binding to Congo red. Surprisingly, the native conformations of insulin and Ig light chain also induced Congo red circular dichroism, but with different spectral shapes than those from fibrils. In fact, a wide variety of native proteins exhibited induced CR circular dichroism indicating that CR bound to representative proteins from different classes of secondary structure such as ␣ (citrate synthase), ␣ ؉ ␤ (lysozyme), ␤ (concavalin A), and parallel ␤-helical proteins (pectate lyase). Partially folded intermediates of apomyoglobin induced different Congo red CD bands than the corresponding native conformation, however, no induced CD bands were observed with unfolded protein. Congo red was also found to induce oligomerization of native proteins, as demonstrated by covalent cross-linking and small angle x-ray scattering. Our data suggest that Congo red is sandwiched between two protein molecules causing protein oligomerization. The fact that Congo red binds to native, partially folded conformations and amyloid fibrils of several proteins shows that it must be used with caution as a diagnostic test for the presence of amyloid fibrils in vitro.In the 1920s Benhold (1) and Divry (2) established that Congo red bound to amyloid in tissue sections and demonstrated its characteristic yellow-green birefringence under crossed polarizers. Since then this birefringence has been used as a diagnostic for amyloid fibrils. The birefringence assay is not a simple one, for example, the tissue sections need to be of a required thickness to show birefringence, reviewed by Elghetany and Saleem (3) and Westermark et al. (4). Congo red binding is not specific for amyloid in the tissue sections, but the assays are performed under extreme conditions with 50 -80% ethanol, high salt and alkaline pH conditions to yield binding to amyloid (5). Despite these extreme conditions, binding to collagen fibers and cytoskeletal proteins results in false-positive results (4). Due to the difficulties with the birefringence assay for in vitro amyloid fibrils, Klunk and co-workers (6, 7) have developed simpler filtration based assays followed by measuring the concentration of free Congo Red to quantify dye binding. The filtration assays would not detect CR 1 bound to soluble monomers or oligomers as they are not large enough to be trapped by 0.2-m filters. Large particles, such as amyloid fibrils, are retained on the filters accounting for the loss of free dye molecules, whereas any native protein molecules bound to CR wou...

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Section: Amyloid Fibrils and Native Conformations Show Differentmentioning

confidence: 68%

Is Congo Red an Amyloid-specific Dye?

Khurana

Uversky

Nielsen

et al. 2001

Journal of Biological Chemistry

295

238

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“…18 It is structurally similar to Congo Red, another promiscuous small molecule that is known to form aggregates and appears to inhibit many enzymes as an aggregate species. 15,27 But suramin does not inhibit our model enzymes (Table 1) and it does not form detectable particles at 400 µM. In a separate comparison, PD98059 is structurally similar to quercetin, an aggregate-forming promiscuous inhibitor (Tables 1 and 3).…”

Section: Discussionmentioning

confidence: 88%

Kinase Inhibitors: Not Just for Kinases Anymore

2003

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Kinase inhibitors are widely employed as biological reagents and as leads for drug design. Their use is often complicated by their lack of specificity. Although binding conserved ATP sites accounts for some of their nonspecificity, some compounds inhibit proteins not known to bind ATP. It has been found that promiscuous hits from high-throughput screening may act as aggregates. To explore whether this mechanism might explain the action of widely used nonspecific kinase inhibitors, 15 such compounds were studied. Eight of these, rottlerin, quercetin, K-252c, bisindolylmaleimide I, bisindolylmaleimide IX, U0126, indirubin, and indigo, inhibited three diverse non-kinase enzymes. Inhibition was time-dependent and sensitive to enzyme concentration; by light scattering, the compounds formed particles of 100-1000 nm diameter. These observations suggest that these eight kinase inhibitors, at least at micromolar concentrations, are promiscuous and act as aggregates. Results obtained from the use of these compounds at micromolar or higher concentrations against individual enzymes should be interpreted cautiously.

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“…4,6,7,27,28 The unusual Congo Red property concerning the possible single molecular 29 and supramolecular complexation suggests that this dye is amenable to attachment to different polymeric conformations, even including occlusion at protein interfaces. 30 However, its binding to β-peptide chains seems favored.…”

Section: Discussionmentioning

confidence: 99%

“…The starting point is the significant difference observed in binding to proteins and self-assembly between the two isomeric dyes, Evans Blue and Trypan Blue. 4,5,7 Studies of these two dyes offer a unique opportunity to approach the mechanism of dye-protein interaction by structural analysis of the ligand.…”

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confidence: 99%