N and C-terminal sub-regions in the c-Myc transactivation region and their joint role in creating versatility in folding and binding.

The proto-oncogene c-myc governs the expression of a number of genes targeting cell growth and apoptosis, and its expression levels are distorted in many cancer forms. The current investigation presents an analysis by proteolysis, circular dichroism, fluorescence and Biacore of the folding and ligand-binding properties of the N-terminal transactivation domain (TAD) in the c-Myc protein. A c-Myc sub-region comprising residues 1-167 (Myc1-167) has been investigated that includes the unstructured c-Myc transactivation domain (TAD, residues 1-143) together with a C-terminal segment, which appears to promote increased folding.

Biophysical properties of regions flanking the bHLH-Zip motif in the p22 Max protein.

The Max protein is the central dimerization partner in the Myc-Max-Mad network of transcriptional regulators, and a founding structural member of the family of basic-helix-loop-helix (bHLH)-leucine zipper (Zip) proteins. Biologically important regions flanking its bHLH-Zip motif have been disordered or absent in crystal structures. The present study shows that these regions are resistant to proteolysis in both the presence and absence of DNA, and that Max dimers containing both flanking regions have significantly higher helix content as measured by circular dichroism than that predicted from the crystal structures.

Site-specific labelling with a metal chelator for protein-structure refinement.

A single free Cys sidechain in the N-terminal domain of the E. coli arginine repressor was covalently derivatized with S-cysteaminyl-EDTA for site-specific attachment of paramagnetic metal ions. The effects of chelated metal ions were monitored with (15)N-HSQC spectra.