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Topogenic signals in integral membrane proteins
1Department of Molecular Biology, Karolinska Institutet, Huddinge, Sweden.
European Journal of Biochemistry
|July 1, 1988
Summary
Integral membrane proteins utilize apolar segments for membrane integration. Charged residues, specifically arginine and lysine, in polar domains dictate the protein's topology, a universal "positive-inside" rule across diverse membranes.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Integral membrane proteins possess apolar segments for lipid bilayer traversal.
- Polar domains adjacent to apolar segments exhibit amino acid compositions similar to soluble proteins.
Purpose of the Study:
- To investigate the amino acid composition of membrane-assembly signals.
- To determine the correlation between polar domain amino acid content and topological information in integral membrane proteins.
Main Methods:
- Analysis of amino acid content in apolar segments from various membrane-assembly signals.
- Correlation analysis of arginyl and lysyl residue content with polar domain location (inside/outside).
Main Results:
- Apolar segments show no significant differences in amino acid content across different membrane proteins.
- A strong correlation exists between the inside/outside location of polar domains and their content of arginyl and lysyl residues.
- This correlation holds true for bacterial inner-membrane proteins and eukaryotic proteins from various organelles (ER, plasma membrane, mitochondria, chloroplasts).
Conclusions:
- The "positive-inside" rule appears to be a universal principle for integral membrane protein topology.
- Apolar regions are crucial for targeting proteins to and integrating them within membranes.
- Charged residues, particularly arginine and lysine, provide essential topological information for membrane protein orientation.