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Intramolecular immunological signal hypothesis revived--structural background of signalling revealed by using Congo Red as a specific tool.

Jagusiak A, Konieczny L, Krol M, Marszalek P, Piekarska B, Piwowar P, Roterman I, Rybarska J, Stopa B, Zemanek G - Mini Rev Med Chem (2015)

Bottom Line: As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade.This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity.These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

View Article: PubMed Central - PubMed

Affiliation: .

ABSTRACT
Micellar structures formed by self-assembling Congo red molecules bind to proteins penetrating into function-related unstable packing areas. Here, we have used Congo red--a supramolecular protein ligand--to investigate how the intramolecular structural changes that take place in antibodies following antigen binding lead to complement activation. According to our findings, Congo red binding significantly enhances the formation of antigen-antibody complexes. As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade. This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity. These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

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MD simulation model explaining the formation of L λ chain Congo red complexes (with dye location in V domains) referred to as“slow” and “ fast” depending on their migration speed under electrophoresis (picture B) and revealing the mechanism by which thebinding locus is rendered susceptible (by displacing or cutting off its N- terminal polypeptide loop – diagrams A and C respectively). Thefigure also presents the subsequent structural effects of dye binding to the V domain of the L chain (right).
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Figure 7: MD simulation model explaining the formation of L λ chain Congo red complexes (with dye location in V domains) referred to as“slow” and “ fast” depending on their migration speed under electrophoresis (picture B) and revealing the mechanism by which thebinding locus is rendered susceptible (by displacing or cutting off its N- terminal polypeptide loop – diagrams A and C respectively). Thefigure also presents the subsequent structural effects of dye binding to the V domain of the L chain (right).

Mentions: Forced rotation of V domains during antigen complexation destabilizes the packing of the N- terminal fragment of the chain, enabling Congo red penetration [19, 20]. This process is accompanied by loosening of the V domain structure, which initially results in partial melting of beta-structural fragments comprising the upper core. Increasing strains overcome the second threshold, expanding the area of instability which eventually engulfs the lower core (Fig. 7). At this stage a fast-migrating complex of the L chain can be formed in the presence of Congo red. As concluded from MD simulation studies, melting of the lower core finally decouples the C-terminal fragment of the polypeptide chain of the V domain, increasing the rotational independence of V and C domains and enabling structural relaxation of the Fab fragment.


Intramolecular immunological signal hypothesis revived--structural background of signalling revealed by using Congo Red as a specific tool.

Jagusiak A, Konieczny L, Krol M, Marszalek P, Piekarska B, Piwowar P, Roterman I, Rybarska J, Stopa B, Zemanek G - Mini Rev Med Chem (2015)

MD simulation model explaining the formation of L λ chain Congo red complexes (with dye location in V domains) referred to as“slow” and “ fast” depending on their migration speed under electrophoresis (picture B) and revealing the mechanism by which thebinding locus is rendered susceptible (by displacing or cutting off its N- terminal polypeptide loop – diagrams A and C respectively). Thefigure also presents the subsequent structural effects of dye binding to the V domain of the L chain (right).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440395&req=5

Figure 7: MD simulation model explaining the formation of L λ chain Congo red complexes (with dye location in V domains) referred to as“slow” and “ fast” depending on their migration speed under electrophoresis (picture B) and revealing the mechanism by which thebinding locus is rendered susceptible (by displacing or cutting off its N- terminal polypeptide loop – diagrams A and C respectively). Thefigure also presents the subsequent structural effects of dye binding to the V domain of the L chain (right).
Mentions: Forced rotation of V domains during antigen complexation destabilizes the packing of the N- terminal fragment of the chain, enabling Congo red penetration [19, 20]. This process is accompanied by loosening of the V domain structure, which initially results in partial melting of beta-structural fragments comprising the upper core. Increasing strains overcome the second threshold, expanding the area of instability which eventually engulfs the lower core (Fig. 7). At this stage a fast-migrating complex of the L chain can be formed in the presence of Congo red. As concluded from MD simulation studies, melting of the lower core finally decouples the C-terminal fragment of the polypeptide chain of the V domain, increasing the rotational independence of V and C domains and enabling structural relaxation of the Fab fragment.

Bottom Line: As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade.This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity.These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

View Article: PubMed Central - PubMed

Affiliation: .

ABSTRACT
Micellar structures formed by self-assembling Congo red molecules bind to proteins penetrating into function-related unstable packing areas. Here, we have used Congo red--a supramolecular protein ligand--to investigate how the intramolecular structural changes that take place in antibodies following antigen binding lead to complement activation. According to our findings, Congo red binding significantly enhances the formation of antigen-antibody complexes. As a result, even low-affinity transiently binding antibodies can participate in immune complexes in the presence of Congo red, although immune complexes formed by these antibodies fail to trigger the complement cascade. This indicates that binding of antibodies to the antigen may not, by itself, fulfill the necessary conditions to generate the signal which triggers effector activity. These findings, together with the results of molecular dynamics simulation studies, enable us to conclude that, apart from the necessary assembling of antibodies, intramolecular structural changes generated by strains which associate high- affinity bivalent antibody fitting to antigen determinants are also required to cross the complement activation threshold.

Show MeSH