David Auble
Below is the structure of an SCF complex in almost its entirety. SCF complexes comprise the largest class of ubiquitin ligases. These ubiquitin ligases are adaptors that bring together a ubiquitin conjugating enzyme (covalently bound to ubiquitin), and a substrate protein that is targeted for ubiquitination. Tethering the enzyme near its substrate is thought to explain the specificity of the ubiquitination reaction. The Cul1 subunit forms an elongated scaffold with other subunits at either end. The Skp1-Skp2 complex interacts with the substrate protein. (This structure shows the F-box portion of Skp2, not the entire protein.) Rbx1 interacts with the ubiquitin conjugating enzyme. While the complex recruits both ubiquitin conjugating enzyme and substrate, because they are separated by the rigid, elongated scaffold (the Rbx1 and Skp1-Skp1 subunits are positioned about 100 angstroms apart), the suggestion is that this architecture is important for positioning particular lysine residues near the active site of the ubiquitin conjugating enzyme in order to get substrates modified at only specific positions.
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Cul1 I Rbx1 I Skp1 I Skp2-F-box |
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