Lfc is a guanine nucleotide exchange factor (GEF) that activates the small GTPase RhoA, and its GEF activity is tightly regulated through protein-protein interactions, phosphorylation, and cellular localization. Lfc is anchored to microtubules through its interaction with the dynein light chain Tctex-1, which results in inhibition of Lfc's GEF activity. Here we present a crystallographic structure of Tctex-1 in complex with Lfc with residues 143-155 of Lfc bound at the Tctex-1 dimer interface. Structural alignment of our structure with Tctex-1 in complex with the dynein intermediate chain (DIC) shows the binding site of the DIC peptide and Lfc substantially overlap. Biochemical evidence, NMR perturbations assays and intrinsic fluorescence provide structural validation and support an extension of the Lfc binding site to the α-helices that may accommodate additional contact points with Tctex-1. We postulate a potential mechanism for Lfc’s recruitment to the microtubules through a tripartite complex with Tctex-1 and DIC.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/42695 |
| Date | 21 November 2013 |
| Creators | Balan, Marc |
| Contributors | Ikura, Mitsuhiko |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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