Leucine-rich repeat

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A leucine-rich repeat (LRR) is a protein structural motif that forms an α/β horseshoe fold. It is composed of repeating 20-30 amino acid stretches that are unusually rich in the hydrophobic amino acid leucine. Typically, each repeat unit has beta strand-turn-alpha helix structure, and the assembled domain, composed of many such repeats, has a horseshoe shape with an interior parallel beta sheet and an exterior array of helices. One face of the beta sheet and one side of the helix array are exposed to solvent and are therefore dominated by hydrophilic residues. The region between the helices and sheets is the protein's hydrophobic core and is tighly sterically packed with leucine residues.

[edit] Examples

Leucine-rich repeat motifs have been identified in a large number of functionally unrelated proteins. The best-known example is the ribonuclease inhibitor, but other proteins such as the tropomyosin regulator tropomodulin also share the motif.

Although the canonical LRR protein contains approximately one helix for every beta strand, variants that form beta-alpha superhelix folds sometimes have long loops rather than helices linking successive beta strands.

[edit] External links

• SCOP LRR fold
• CATH Alpha-beta horseshoe architecture

[edit] References

• Branden C, Tooze J. (1999). Introduction to Protein Structure 2nd ed. Garland Publishing: New York, NY.

Protein tertiary structure
General:	Structural domain | Protein folding
All-α folds:	Helix bundle | Globin fold | Homeodomain fold | Alpha solenoid
All-β folds:	Immunoglobulin fold | Beta barrel | Beta-propeller domain
α/β folds:	TIM barrel | Leucine-rich repeat | Flavodoxin fold | Thioredoxin fold | Trefoil knot fold
α+β folds:	Ferredoxin fold | Ribonuclease A | SH2-like fold
Irregular folds:	Conotoxin
←Secondary structure	Structure determination methods	Quaternary structure→