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Modeling a dehalogenase fold into the 8-A density map for Ca(2+)-ATPase defines a new domain structure
1Skirball Institute of Biomolecular Research, Department of Cell Biology, New York University School of Medicine, New York, New York 10016, USA. stokes@saturn.med.nyu.edu
Biophysical Journal
|March 29, 2000
Summary
Researchers propose a new structural model for calcium ATPase (Ca2+-ATPase) based on homology with hydrolases. This model reveals a novel domain structure and suggests a mechanism for ATP hydrolysis driving ion transport.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- P-type pumps are crucial for maintaining cellular ion gradients via active transport.
- Previous low-resolution structures lacked detail on cytoplasmic domains of P-type pumps.
Purpose of the Study:
- To elucidate the detailed architecture of cytoplasmic domains in Ca2+-ATPase.
- To propose a novel structural model for Ca2+-ATPase based on homology.
Main Methods:
- Extended sequence comparisons within the hydrolase superfamily.
- Delineated domains within the 8-Å density map of Ca2+-ATPase.
- Fitted the atomic structure of L-2 haloacid dehalogenase into the Ca2+-ATPase model.
Main Results:
- Identified a new domain structure for Ca2+-ATPase, with the phosphorylation domain adopting a Rossmann fold.
- The model suggests two ATP binding sites at the interface between domains.
- Predicted the configuration of Mg.ATP and proposed a mechanism for initiating domain movements.
Conclusions:
- The proposed model reconciles existing mutagenesis and cross-linking data.
- A novel mechanism involving Mg2+ liganding changes is proposed for coupling ATP hydrolysis to ion transport.
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