Hidden disorder propensity of the N-terminal segment of universal adapter protein 14-3-3 is manifested in its monomeric form: Novel insights into protein dimerization and multifunctionality

作者：Sluchanko Nikolai N^*; Uversky Vladimir N

来源：Biochimica et Biophysica Acta-Proteins and Proteomics, 2015, 1854(5): 492-504.

DOI：10.1016/j.bbapap.2015.02.017

• 14-3-3 proteins
• Phosphorylation
• Intrinsically disordered protein
• Circular dichroism spectroscopy
• X-ray scattering
• Ensemble optimization method (EOM)

The multiplicity of functions of 14-3-3 proteins, integrated into many cellular interactions and signaling networks, is primarily based upon their dimeric alpha-helical structure that is capable of binding phosphorylated protein partners as well as displaying a "moonlighting" chaperone-like activity. The structure and functions of 14-3-3 proteins are regulated in different ways, including Ser58 phosphorylation in the interface, which shifts equilibrium towards the formation of protein monomers whose role is poorly understood. While modification of Ser58 induced only partial dissociation, the engineered triple mutation of human 14-3-3 zeta located in the first alpha-helix deeply monomerized the protein, allowing for a structural analysis of the monomeric form. Dimer-incapable 14-3-3 proteins retained binding capacity and specificity towards some phosphopartners, and also demonstrated increased chaperone-like activity on various substrates. Here, we found a substantial propensity of the N-terminal segment (similar to 40 residues) of 14-3-3 proteins to intrinsic disorder, showing remarkable conservation across different isoforms and organisms. We hypothesized that this intrinsic disorder propensity, hidden in the et-helical 14-3-3 dimer, can be manifested upon its dissociation and interrogated novel monomeric 14-3-3 zeta carrying both monomerizing and S58E mutations (14-3-3 zeta mS58E). CD spectroscopy showed that, at physiological temperatures, this protein has similar to 10-15% reduced helicity relative to the wild type protein, corresponding to roughly 40 residues. Along with the known flexibility of C-terminus, SAXS-based modeling of the 14-3-zeta mS58E structure strongly suggested pliability of its N-terminus. The unraveled disorder propensity of the N-terminal tails of 14-3-3 proteins provides new clues for better understanding of the molecular mechanisms of dimerization and multifunctionality of these universal adapter proteins.

• 出版日期2015-5