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KH domain: one motif, two folds
1Howard Hughes Medical Institute and Department of Biochemistry, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9050, USA. grishin@chop.swmed.edu
Nucleic Acids Research
|February 13, 2001
Summary
The K homology (KH) domain, a common RNA-binding motif, shows similar sequences but different structures in proteins like hnRNP K and S3. This suggests protein folds can evolve through extensions and rearrangements.
Area of Science:
- * Molecular Biology
- * Structural Biology
- * Evolutionary Biology
Background:
- * The K homology (KH) domain is a prevalent RNA-binding motif found in various proteins.
- * Proteins like heterogeneous nuclear ribonucleoprotein K (hnRNP K) and ribosomal protein S3 contain KH domains.
Purpose of the Study:
- * To investigate the structural diversity of KH domains despite sequence similarity.
- * To understand the evolutionary pathways leading to different protein folds within the KH motif family.
Main Methods:
- * Comparative analysis of spatial structures of KH domains from hnRNP K and S3.
- * Examination of sequence similarities within KH motif regions.
Main Results:
- * KH domains in hnRNP K and S3 exhibit topologically dissimilar structures, belonging to different protein folds.
- * This represents a rare instance of significant sequence similarity coexisting with globally distinct structures in protein domains.
- * Evolutionary scenarios involving N- and C-terminal extensions or modifications of existing topologies are proposed.
Conclusions:
- * Protein folds can diverge significantly even when sharing sequence similarity in key motifs.
- * Evolutionary mechanisms like strand insertion/deletion can drive major structural changes, similar to serpins.
- * The study provides insights into protein fold evolution and the plasticity of protein structures.