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The tetratricopeptide repeat (TPR) domain mediates inter-protein associations in a number of systems. The domain is also thought to mediate oligomerization of some proteins, but this has remained controversial, with conflicting data appearing in the literature. By way of investigating such TPR-mediated self-associations we used a variety of biophysical techniques to characterize purified recombinant Sgt1, a TPR-containing protein found in all eukaryotes that is involved in a broad range of biological processes, including kinetochore assembly in humans and yeast and disease resistance in plants. We show that recombinant Sgt1 from Arabidopsis, barley, and yeast self-associates in vitro while recombinant human Sgt1 does not. Further experiments on barley Sgt1 demonstrate unambiguously a TPR-mediated dimerization, which is concentration- and ionic-strength-dependent and results in a global increase in helical structure and stability of the protein. Dimerization is also redox sensitive, being completely abolished by the formation of an intramolecular disulfide bond where the contributing cysteines are conserved in plant Sgt1s. The dimer interface was mapped through cross-linking and mass spectrometry to the C-terminal region of the TPR domain. Our study, which provides the first biophysical characterization of plant Sgt1, highlights how TPR domains can mediate self-association in solution and that sequence variation in the regions involved in oligomerization affects the propensity of TPR-containing proteins to dimerize.

Original publication

DOI

10.1021/bi700735t

Type

Journal article

Journal

Biochemistry

Publication Date

09/10/2007

Volume

46

Pages

11331 - 11341

Keywords

Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Arabidopsis Proteins, Cell Cycle Proteins, Chromatography, Gel, Circular Dichroism, Dimerization, Glucosyltransferases, Hordeum, Humans, Mass Spectrometry, Models, Molecular, Molecular Sequence Data, Plant Proteins, Protein Structure, Secondary, Protein Structure, Tertiary, Repetitive Sequences, Amino Acid, Repressor Proteins, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid