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Structural properties of the microsomal triglyceride-transfer protein complex.
J R Wetterau1, L P Aggerbeck, P M Laplaud
1Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Ohio 45267-0575.
Biochemistry
|May 7, 1991
Summary
The microsomal triglyceride-transfer protein (MTP) is a stable 1:1 complex of protein disulfide isomerase (PDI) and an 88K polypeptide. This complex, with a molecular weight of 150,000, exhibits an asymmetric structure and plays a key role in lipid transport.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Chemistry
Background:
- Microsomal triglyceride-transfer protein (MTP) facilitates lipid transport.
- MTP is known to be a complex containing protein disulfide isomerase (PDI).
Purpose of the Study:
- To elucidate the structural composition and stoichiometry of the MTP complex.
- To define the functional roles of MTP's structural elements.
Main Methods:
- Sedimentation equilibrium experiments to determine molecular weight.
- SDS-polyacrylamide gel electrophoresis and Coomassie Blue staining for subunit quantification.
- Analytical ultracentrifugation and gradient gel electrophoresis for hydrodynamic properties.
- Circular dichroism spectroscopy for secondary structure analysis.
Main Results:
- MTP molecular weight determined to be 150,000.
- Confirmed a 1:1 stoichiometry between PDI and an 88,000 molecular weight polypeptide (88K).
- MTP complex is asymmetric with a high water of hydration.
- PDI and 88K form a stable complex.
- MTP secondary structure analysis revealed ~28% alpha-helix and ~28% beta-structure.
Conclusions:
- MTP is a stable heterodimer composed of PDI and an 88K subunit.
- The structural characteristics of MTP suggest specific functional implications in lipid transfer.