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The immunoglobulin fold family: sequence analysis and 3D structure comparisons
D M Halaby1, A Poupon, J Mornon
1Systèmes Moléculaires et Biologie Structurale, LMCP, CNRS UMR C7590 Universités Pierre et Marie Curie (P6) et Denis Diderot (P7), Tour 16,Case 115, 4 Place Jussieu, 75252 Paris cedex 05, France.
Protein Engineering
|August 6, 1999
Summary
The immunoglobulin fold family (IgFF) shows conserved 3D structures despite diverse sequences. This structural conservation, particularly in hydrophobic cores, explains how unrelated proteins adopt similar folds and suggests new classification subtypes.
Area of Science:
- Structural Biology
- Bioinformatics
- Protein Evolution
Background:
- The immunoglobulin fold family (IgFF) comprises distantly related proteins sharing the immunoglobulin (Ig) fold.
- These proteins exhibit significant heterogeneity in tissue distribution, species, and function.
- Despite sequence diversity, the 3D structures of Ig-like domains are highly conserved.
Purpose of the Study:
- To classify Ig-like domains based on secondary structure conservation.
- To analyze the correlation between conserved sequences and structures within the IgFF.
- To propose new classification subtypes and understand evolutionary processes in the IgFF.
Main Methods:
- Multiple structural alignment of conserved common cores of 52 Ig-like domain structures.
- Analysis of topologically equivalent residues and hydrophobic common cores.
- Sequence and structure analysis to identify evolutionary patterns and propose new classifications.
Main Results:
- Defined topologically equivalent residues and described hydrophobic common cores in Ig-like domains.
- Identified that 3D structures are more conserved than sequences across the IgFF.
- Proposed two new subtypes (C3, C4) and a global structural classification for the IgFF.
- Observed low sequence identity between subgroups, indicating divergent and convergent evolution.
Conclusions:
- Hydrophobic residues in common cores are crucial for maintaining the Ig fold despite sequence divergence.
- Structural conservation explains the functional and evolutionary diversity of the IgFF superfamily.
- The study proposes an updated classification system for Ig-like domains based on structural evidence.