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Differences in the metal ion structure between Sr- and Ca-prothrombin fragment 1
T P Seshadri1, E Skrzypczak-Jankun, M Yin
1Department of Chemistry, Michigan State University, East Lansing 48824.
Biochemistry
|February 8, 1994
Summary
Strontium-prothrombin fragment 1 reveals a unique polymeric array of strontium ions interacting with gamma-carboxyglutamic acid residues. These interactions differ from calcium-bound fragment 1, suggesting distinct roles in biological processes.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Prothrombin fragment 1 plays a crucial role in blood coagulation.
- Understanding the structural basis of metal ion binding is key to elucidating its function.
Purpose of the Study:
- To determine the high-resolution crystal structure of strontium-prothrombin fragment 1.
- To compare the strontium-bound structure with the previously determined calcium-bound structure.
Main Methods:
- X-ray crystallography at 2.5-Å resolution.
- Restrained least-squares refinement.
- Structural comparison with Ca-fragment 1.
Main Results:
- The Sr-prothrombin fragment 1 structure shows a polymeric array of five Sr2+ ions bound to gamma-carboxyglutamic acid (Gla) residues.
- Significant differences in Sr2+ and Ca2+ coordination were observed, including lack of water coordination with Sr2+.
- A novel Sr2+ ion binding site was identified, potentially involved in phospholipid interactions.
- An oligosaccharide moiety was located near Asn101, exhibiting flexible disorder.
Conclusions:
- Strontium binding to prothrombin fragment 1 creates distinct structural features compared to calcium binding.
- The identified Sr2+ ion binding sites may mediate unique interactions relevant to prothrombin function.
- These findings provide insights into the structural plasticity of Gla-rich domains in response to different divalent cations.