David Auble
Many proteins contain repeated structural elements that form large surfaces for protein recognition. Here you see examples of these. Leucine-rich repeat (LRR) proteins form alpha-beta superhelical structures whereas HEAT and ARM proteins possess repeats of a helix-turn-helix structural motif. The default cartoon representations allow you to see the overall folds of the repeats. In the space-filling models it's perhaps easier to appreciate the extensive surface areas involved in protein-protein binding. Notice that angiogenin does not bind symmetrically to the superhelical cleft as one might have imagined by looking at the structure of ribonuclease inhibitor alone.
1a4y shows the complex between ribonuclease inhibitor, an LRR protein, and angiogenin.
1qgr shows the complex between importin β and the IBB domain of importin α. Importin β is an ARM repeat protein.
1b3u shows the structure of human protein phosphatase 2A 65 kD α regulatory subunit, a HEAT repeat protein.
1w8a shows the structure of the third LRR domain of Drosophila SLIT, a signaling protein.
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1a4y ribonuclease inhibitor I angiogenin |
1qgr importin β I importin α |
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1b3u PP2A PR65α |
1w8a LRR domain of SLIT |
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