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Intersubunit fluorescence energy transfer in human factor VIII
1Department of Medicine, University of Rochester School of Medicine and Dentistry, New York 14642.
The Journal of Biological Chemistry
|August 25, 1989
Summary
This study investigated the spatial relationship between heavy and light chains in human factor VIII (FVIII). Findings reveal a close proximity between the A2 domain of the heavy chain and the A3 domain of the light chain in FVIII heterodimers.
Area of Science:
- Biochemistry
- Molecular Biology
- Hematology
Background:
- Human factor VIII (FVIII) is essential for blood coagulation.
- FVIII circulates as a heterodimer of heavy and light chains.
- Understanding FVIII subunit interactions is crucial for elucidating its function.
Purpose of the Study:
- To determine the spatial relationship between the heavy and light chains of human factor VIII.
- To identify specific cysteine residues involved in subunit association.
- To correlate subunit proximity with FVIII clotting activity.
Main Methods:
- Modification of purified FVIII subunits with sulfhydryl-specific fluorophores.
- Identification of fluorophore attachment sites using amino-terminal sequencing.
- Measurement of subunit reassociation via fluorescence energy transfer (FRET).
- Correlation of FRET data with FVIII clotting activity assays.
Main Results:
- Identified Cys528 on the heavy chain (A2 domain) and Cys1858 on the light chain (A3 domain) as attachment sites.
- Demonstrated that donor fluorescence quenching parallels FVIII clotting activity.
- Calculated a distance of 20 Å between the fluorophores on the heavy and light chains.
- Observed saturable reassociation with respect to heavy chain concentration.
Conclusions:
- Established a close spatial relationship between the A2 domain of the FVIII heavy chain and the A3 domain of the light chain.
- Provided direct evidence for the proximity of these domains in the active FVIII heterodimer.
- Linked subunit proximity to functional FVIII clotting activity.