The human genome encodes 69 different F-box proteins (FBPs), each of which can potentially assemble with Skp1-Cul1-RING to serve as the substrate specificity subunit of an SCF ubiquitin ligase complex. SCF activity is switched on by conjugation of the ubiquitin-like protein Nedd8 to Cul1. Cycles of Nedd8 conjugation and deconjugation acting in conjunction with the Cul1-sequestering factor Cand1 are thought to control dynamic cycles of SCF assembly and disassembly, which would enable a dynamic equilibrium between the Cul1-RING catalytic core of SCF and the cellular repertoire of FBPs. To test this hypothesis, we determined the cellular composition of SCF complexes and evaluated the impact of Nedd8 conjugation on this steady-state. At least 42 FBPs assembled with Cul1 in HEK 293 cells, and the levels of Cul1-bound FBPs varied by over two orders of magnitude. Unexpectedly, quantitative mass spectrometry revealed that blockade of Nedd8 conjugation led to a modest increase, rather than a decrease, in the overall level of most SCF complexes. We suggest that multiple mechanisms including FBP dissociation and turnover cooperate to maintain the cellular pool of SCF ubiquitin ligases.
Pubmed ID: 21169563 RIS Download
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A collection of both commercial and noncommercial software products which includes: Mascot Distiller, Mascot Parser, and Mascot Server. Mascot Distiller is commercial and provides a single interface to process raw data into de-isotoped peak lists. This tool can also be used for the easy distribution of search and quantitative results to colleagues. The non-commercial Mascot Parser software provides an API (Application Programmer Interface) that makes it easier to access search results written in C++, Java, Python and Perl. Mascot Server is non-commercial, and is a collection of peptide mass fingerprints as well as a MS/MS database. A selection of popular sequence databases are available online and include SwissProt, NCBInr, and the EST divisions of EMBL. This server is best used for evaluating and searching for smaller data sets.
View all literature mentionsData set of connection probabilities and PSP amplitudes from Chapeton, J., Fares, T., LaSota, D., and Stepanyants, A., Efficient associative memory storage in cortical circuits of inhibitory and excitatory neurons, PNAS, 109(51): E3614E3622 (2012). Available as a PDF under Resources tab.
View all literature mentionsA quantitative proteomics software package for analyzing large-scale mass-spectrometric data sets. It is a set of algorithms that include peak detection and scoring of peptides, mass calibration, database searches for protein identification, protein quantification, and provides summary statistics.
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