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Mapping of functional domains in the plasma membrane Ca2+ pump using trypsin proteolysis
E Zvaritch1, P James, T Vorherr
1Laboratory for Biohemistry, Swiss Federal Institute of Technology (ETH), Zurich.
Biochemistry
|September 4, 1990
Summary
Researchers mapped fragments of the erythrocyte Ca2+ pump using trypsin digestion and sequencing. This detailed structural analysis identified specific domains, including the calmodulin-interacting region and the acidic phospholipid-binding site.
Area of Science:
- Biochemistry
- Molecular Biology
- Membrane Protein Structure
Background:
- The erythrocyte Ca2+ pump (Ca2+/H+-ATPase) is crucial for maintaining calcium homeostasis.
- Previous studies have begun to elucidate the domain organization of this essential ion transporter.
Purpose of the Study:
- To further delineate the structural organization of the purified erythrocyte Ca2+ pump.
- To identify the locations of specific functional domains within the pump's primary sequence.
Main Methods:
- Proteolytic digestion of the purified Ca2+ pump with trypsin.
- Analysis of resulting protein fragments using SDS-polyacrylamide gel electrophoresis.
- N- and C-terminal sequencing of isolated fragments blotted onto PVDF membranes.
Main Results:
- Four major fragments (90, 85, 81, and 76 kDa) and a 33 kDa fragment were generated by trypsin digestion.
- N- and C-terminal sequencing localized these fragments within the overall Ca2+ pump structure.
- The calmodulin-interacting domain was further characterized, and the acidic phospholipid-binding domain was tentatively placed between transmembrane helices 2 and 3.
Conclusions:
- The study provides a refined map of the erythrocyte Ca2+ pump's domain organization.
- Specific functional regions, including those interacting with calmodulin and acidic phospholipids, have been localized within the protein structure.