Conformational Specifics of TPR Motifs from SGT

 

Ming-Tao Pai1, Chih-Sheng Yang1, Shiou-Ru Tzeng1, Chung Wang2, Jya-Wei Cheng1

1Department of Life Science, Tsing Hua University, Hsinchu, Taiwan; 2Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan

 

The tetratricopeptide repeat (TPR) motifs exist in a variety of proteins that are, in many cases, part of multiprotein assemblies. The TPR motif contains 34 degenerate amino acids and was found in 3-16 copies in wide range of functionally different proteins. TPR-containing proteins play an important role in the regulation of cell-cycle, transcription, mitochondrial and peroxisomal protein transport, neurogenesis, protein kinase inhibition, and chaperone. Here we report conformational properties of the TPR motifs from human small glutamine-rich tetratricopeptide repeat-containing protein (SGT). By four lines of evidences (size-exclusion chromatography, translational diffusion coefficient, chemical cross-linking, and surface plasmon resonance) we could demonstrate that three TPR motifs of human SGT exists a monomer-dimer equilibrium. From SPR we could deduce the dissociation constant (342 μM at 25). The stability of SGT TPR motifs was determined by circular dichroism and fluorescence spectroscopy. Furthermore, the SGT TPR motifs bind to the C-terminal of a negatively charged HSC70 peptide. These results are discussed in terms of a homology model of TPR motifs of SGT, based on the three dimensional structure of the TPR domain of protein phosphatase 5.

 

Acknowledgment: This work is supported by grants from the National Science Council, ROC.