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Discontinuous membrane helices in transport proteins and their correlation with function
Emanuela Screpanti1, Carola Hunte
1Department Molecular Membrane Biology, Max-Planck-Institute of Biophysics, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany.
Journal of Structural Biology
|March 14, 2007
Summary
Integral membrane proteins can feature "discontinuous" helices, where a peptide chain interrupts the helical structure. This helix-peptide-helix motif is crucial for ion transport in various transporters.
Area of Science:
- Structural biology
- Membrane protein architecture
Background:
- Integral membrane proteins typically form alpha-helical bundles or beta-barrels.
- Emerging structural data reveal irregular motifs, including discontinuous helices.
Purpose of the Study:
- To investigate the structural characteristics of discontinuous helices in ion-transporting membrane proteins.
- To correlate specific structural motifs with ion translocation function.
Main Methods:
- Analysis of determined protein structures, including Ca(2+)-ATPase, NhaA, LeuT(Aa), ClC H(+)/Cl(-) exchanger, and Glt(Ph).
- Examination of helical structure interruptions and associated polypeptide chains.
Main Results:
- Discontinuous helices, interrupted by extended peptides, are present in active ion transporters.
- These motifs are integrated as transmembrane or hairpin segments.
- Secondary transporters exhibit inverted internal duplication domains with weak sequence correlation, involving discontinuous helices.
- The helix-peptide-helix motif is directly correlated with ion translocation.
Conclusions:
- The helix-peptide-helix motif, with its extended peptides and specific residues, forms the basis for ion recognition, binding, and translocation.
- This structural motif is a key functional element in diverse ion transporters.
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