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Title: Dissecting interactions within focal adhesions : studies on vinculin
Author: Cox, Clare Louise
ISNI:       0000 0004 2673 570X
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2008
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Vinculin and paxillin are proteins that localise to focal adhesions. Focal adhesions are specialised sites of cell attachment between the cytoplasmic side of the cell membrane and the extracellular matrix. They consist of receptors that link extracellular matrix ligands to the actin cytoskeleton via various protein assemblies. They act as mechanical links and as sites of signal transduction to transduce signals for cell locomotion, cell attachment and detachment, apoptosis and gene expression. A range of cellular responses depend critically on the composition and regulation of focal adhesions. Vinculin and paxillin will interact in vitro. The tail domain of vinculin interacts with a motif on paxillin called an LD motif. The interaction between LD motifs and their target proteins is important for regulation of focal adhesion signalling, yet little is known regarding recognition mechanisms between LD domains and interaction partners. In this thesis, the molecular nature of the vinculin tail (Vt) and paxillin LD motif interaction has been studied using purified Vt, synthesised LD peptide mimics and recombinant paxillin His-LD1/LD2. The 1H-15N-HSQC spectrum of a Vt/I997S mutant has been assigned and the NH assignments transferred to a wild-type Vt spectrum. Chemical shift perturbation studies have subsequently been undertaken using wild-type Vt and paxillin. The data presented here is consistent with specificity for LD motifs and points to an interaction between Vt and LD1 and LD2. In contrast there is little or no interaction with LD4. Two binding models are proposed; a single binding site on Vt face 3-4 where LD motifs bind in an extended conformation, or a two-site binding on Vt face 3-4 with two LD motifs bound as a-helices. Both models need further analysis. NMR data for the paxillin His-LD1/LD2 construct suggests a predominantly unstructured molecule in solution that can catalyse precipitation of Vt when Vt is added to excess. It is clear that the mechanism of interaction between Vt and paxillin LD motifs is distinct from that of focal adhesion kinase interacting with paxillin. Further investigation is required to elucidate the precise mechanism of binding. A comparison of this data with other LD-protein interactions suggests there are little similarities between the target sequences that LD motifs recognise and that target proteins can be structurally different.
Supervisor: Werner, Jorn Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH301 Biology