SCF complexes

Remarkably, at the same time, several groups independently determined that there was a previously undiscovered component to the SCF complex - a small non-canonical RING finger protein known variably as Rbxl, Rod or Hrtl [36-... 

Kus, B., Caldon, C. E., Andorn-Broza, R., and Edwards, A. M. Functional interactions of 13 yeast SCF complexes with a set of yeast F2 enzymes in vitro. Proteins Structure, Function, and Bioinformatics 2004, 54, 455-67. 

The essential components of the SCF ubiquitin E3 ligase include Skpl, Cul-1/ Cdc53, one of many F-box proteins, and the RINC-H2-finger protein Rod (Rbxl or Hrtl) (Figure 6.2). Although initial studies did not reveal the presence of a fourth component of the SCF complex [14, 15], later work showed that a RINC-H2-finger protein, Rod, is an essential subunit of the SCF complex [3]. The SCF complex thus contains three invariable components (Rod, Cull, and Skpl) which provide a core structure to which one of the many substrate-specific subunits (F-box proteins) binds. The Rocl-Cull-Skpl core also independently interacts with the ubiquitin E2-conjugating enzyme to couple ubiquitin transfer to the substrates [3]. One of the E-box proteins binds directly to a specific substrate and such interaction facilitates the polyubiquitination of the substrate by ubiquitin... 

In the SCF complex, Cull forms the core scaffold that associates with Rod at the extreme C-terminal region [3]. At its the amino terminal region, Cull interacts... 

Several mechanisms have been shown to regulate the activity of the SCF complex. The expression of F-box proteins such as Skp2 is regulated by cell-cycle-dependent transcription [4]. The expression of Skp2 is high in late Gl, S, and G2/M phase but... 

Another level of control is mediated through the control of F-box protein stabilities by the SCF complex using an auto-ubiquitination mechanism. Deletion of the F-box motif of various F-box proteins such as yeast Cdc4 or j5-Trcp abolishes the interaction between Skpl/Cull and the F-box proteins [66]. Consequently the F-box proteins become more stable. This regulation may provide a means to recycle the components of SCF complexes between different F-box proteins. In addition, the levels of a particular F-box protein may be in part regulated by the balance between autoubiquitination and substrate-specific ubiquitination and thus could be sensitive to the presence of the substrates. 

The SCF Complex and the Related Cullin-containing Ubiquitin E3 Ligase 1151... 

SCF -CyclinE-E2 complexes [66, 85, 103]. In all cases, no intermolecular collision was found in the final models. The substrate-binding domains of all three F-box proteins are positioned on the same side of the SCF complex as the E2. In addition, these domains are all oriented toward the E2 active site. Remarkably, the positions of the WD40 domain in the and SCF models are strikingly... 

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