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During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
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Analyzing the Interaction of Fluorescent-Labeled Proteins with Artificial Phospholipid Microvesicles using Quantitative Flow Cytometry
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Single-chain factor XII exhibits activity when complexed to polyphosphate.

R Engel1, C M Brain, J Paget

  • 1Faculty of Biological Sciences, University of Leeds, Leeds, UK.

Journal of Thrombosis and Haemostasis : JTH
|July 22, 2014
PubMed
Summary

Platelet polyphosphate (polyP70) activates factor XII (FXII) autoactivation through a single-chain intermediate (scFXII-polyP70). This pathway is crucial for initiating contact activation in vivo, acting on physiological substrates like FXI and prekallikrein.

Keywords:
blood coagulationfactor XIIhemostasispolyphosphateszymogens

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Area of Science:

  • Biochemistry
  • Hematology
  • Molecular Biology

Background:

  • Factor XII (FXII) autoactivation mechanisms were initially studied using non-physiological surfaces.
  • Natural anionic activating surfaces, like platelet polyphosphate (polyP), have been identified.

Purpose of the Study:

  • To investigate the autoactivation of FXII induced by polyP with a length similar to that found in platelets (polyP70).

Main Methods:

  • Comparative analysis of FXII autoactivation using polyP70 and dextran sulfate (DS).
  • Western blotting to identify different forms of activated FXII.
  • Enzyme kinetics and inhibition studies to characterize scFXII-polyP70 activity.

Main Results:

  • PolyP70 demonstrated efficacy in FXII autoactivation, forming single-chain FXII (scFXII).
  • scFXII-polyP70 exhibited reversible activity, enhanced by Zn(2+), and showed cooperative substrate binding.
  • scFXII-polyP70 effectively activated FXI and prekallikrein.

Conclusions:

  • Platelet-derived polyP70 facilitates FXII autoactivation via an active single-chain intermediate.
  • scFXII-polyP70 plays a significant role in initiating contact activation in vivo.