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3(10)-Helix adjoining alpha-helix and beta-strand: sequence and structural features and their conservation
Lipika Pal1, Bhaskar Dasgupta, Pinak Chakrabarti
1Bioinformatics Centre, Bose Institute, P-1/12 CIT Scheme VIIM, Calcutta 700 054, India.
Biopolymers
|March 11, 2005
Summary
Protein structure analysis reveals that adjacent helices influence amino acid sequences. Composite helices, like 3(10)-alpha, show altered residue preferences and structural bends, impacting protein folding.
Area of Science:
- Structural Biology
- Biophysics
- Protein Science
Background:
- Alpha-helices and 3(10)-helices are common secondary structures in proteins.
- The interface between different secondary structural elements can influence protein folding and stability.
- Understanding composite helix formation is crucial for predicting protein structure and function.
Purpose of the Study:
- To investigate how the presence of an adjacent 3(10)-helix affects amino acid composition at the termini of an alpha-helix.
- To determine if a single helical cylinder can accurately represent composite helices (e.g., 3(10)-alpha and alpha-3(10)).
- To analyze the conservation and structural context of composite helices involving beta-strands.
Main Methods:
- Analysis of known protein structures from the Protein Data Bank.
- Identification and characterization of 3(10)-alpha and alpha-3(10) composite helices.
- Examination of amino acid preferences at helix termini and junctional regions.
- Comparison of structural features and conservation of different composite helix types.
Main Results:
- The preceding secondary structural element influences the sequence of the subsequent element.
- Proline preference shifts in alpha-helices adjacent to 3(10)-helices.
- Composite helices exhibit bends at junctions, particularly 3(10)-alpha, affecting tertiary structure.
- Beta-strand-3(10)-helix composites are more conserved than helix-helix composites.
- 3(10)-helices often form loops in beta-hairpin or beta-beta-corner motifs.
Conclusions:
- Composite helices are not always accurately represented by a single helical cylinder due to junctional bends.
- These bends contribute to globular protein folding, similar to proline-induced kinks.
- The overall protein fold may be more conserved than the specific secondary structure elements within composites.
- 3(10)-helix involvement in beta-strand composites suggests a role in conserved structural motifs.